String Functions for Data Manipulation

Estimated reading: 4 minutes 85 views

String Functions for Data Manipulation in SQL for Software Testing

String functions in SQL allow testers to manipulate, format, and analyze text data stored in database columns. These functions are essential for validating data transformations, ensuring correct formatting, and testing application logic that depends on textual data.

What Are String Functions in SQL?

String functions operate on text data types like VARCHAR, CHAR, or TEXT. They help extract, modify, and analyze string values stored in a database.

Common String Functions in SQL:

CONCAT: Combines two or more strings.
SUBSTRING: Extracts part of a string.
LENGTH: Returns the length of a string.
UPPER and LOWER: Converts a string to uppercase or lowercase.
TRIM, LTRIM, RTRIM: Removes whitespace or specific characters.
REPLACE: Replaces occurrences of a substring.
LEFT and RIGHT: Extracts characters from the left or right of a string.
INSTR: Finds the position of a substring.
REVERSE: Reverses a string.

Key Uses of String Functions in Software Testing

1. Validating Data Format

String functions help testers ensure that textual data follows the required format.

Example: Check if email addresses are lowercase:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>LOWER<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>lowercase_email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>users<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-WHERE"</span><span class="token operator">&gt;</span><span class="token keyword keyword-WHERE">WHERE</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>operator"</span><span class="token operator">&gt;</span><span class="token operator">&amp;</span>lt<span class="token punctuation">;</span><span class="token operator">&amp;</span>gt<span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>LOWER<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Ensure that email addresses are consistently stored in lowercase format.

2. Extracting Substrings

Testers can extract specific parts of a string for validation.

Example: Extract the domain from email addresses:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>SUBSTRING<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>INSTR<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>email<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>string"</span><span class="token operator">&gt;</span><span class="token string">'@'</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>operator"</span><span class="token operator">&gt;</span><span class="token operator">+</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>number"</span><span class="token operator">&gt;</span><span class="token number">1</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>domain<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>users<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Validate that email addresses belong to allowed domains.

3. Combining Strings

Testers use CONCAT to simulate full names or formatted output.

Example: Combine first and last names into full names:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>CONCAT<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>first_name<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>string"</span><span class="token operator">&gt;</span><span class="token string">'&lt;span<span class="token space"> </span>class="token<span class="token space"> </span>space"&gt;<span class="token space"> </span>&lt;/span&gt;'</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>last_name<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>full_name<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>employees<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Verify that the application correctly displays full names.

4. Ensuring Data Consistency

String functions like TRIM and REPLACE help clean up inconsistent data.

Example: Remove extra spaces from user names:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>TRIM<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>username<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>cleaned_username<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>users<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Ensure that user input is sanitized and stored correctly.

5. Finding Patterns in Data

Functions like INSTR help identify patterns or validate substrings.

Example: Find users with phone numbers containing a specific area code:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>phone<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>contacts<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-WHERE"</span><span class="token operator">&gt;</span><span class="token keyword keyword-WHERE">WHERE</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>INSTR<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>phone<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>string"</span><span class="token operator">&gt;</span><span class="token string">'123'</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>operator"</span><span class="token operator">&gt;</span><span class="token operator">&amp;</span>gt<span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>number"</span><span class="token operator">&gt;</span><span class="token number">0</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Validate that phone numbers include required prefixes or codes.

6. Replacing Substrings

Testers use REPLACE to verify or manipulate specific parts of a string.

Example: Replace old product codes with new ones:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-REPLACE"</span><span class="token operator">&gt;</span><span class="token keyword keyword-REPLACE">REPLACE</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>product_code<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>string"</span><span class="token operator">&gt;</span><span class="token string">'OLD'</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>string"</span><span class="token operator">&gt;</span><span class="token string">'NEW'</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>updated_code<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>products<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Confirm that the application updates product codes correctly.

7. Analyzing String Length

The LENGTH function ensures that strings meet length constraints.

Example: Find usernames exceeding a length limit:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>username<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>users<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-WHERE"</span><span class="token operator">&gt;</span><span class="token keyword keyword-WHERE">WHERE</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>LENGTH<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>username<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>operator"</span><span class="token operator">&gt;</span><span class="token operator">&amp;</span>gt<span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>number"</span><span class="token operator">&gt;</span><span class="token number">20</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Validate that user inputs comply with length restrictions.

8. Converting Case

UPPER and LOWER functions ensure consistent text formatting.

Example: Convert product names to uppercase for display:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>UPPER<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>product_name<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>uppercase_name<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>products<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Verify that product names are displayed in a consistent format.

9. Reversing Strings

Testers can reverse strings for specific validation scenarios.

Example: Check if a string is a palindrome:

<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-SELECT"</span><span class="token operator">&gt;</span><span class="token keyword keyword-SELECT">SELECT</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>string<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">,</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>REVERSE<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>string<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-AS"</span><span class="token operator">&gt;</span><span class="token keyword keyword-AS">AS</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>reversed_string<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-FROM"</span><span class="token operator">&gt;</span><span class="token keyword keyword-FROM">FROM</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>test_table<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>keyword<span class="token space"> </span>keyword-WHERE"</span><span class="token operator">&gt;</span><span class="token keyword keyword-WHERE">WHERE</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>string<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>operator"</span><span class="token operator">&gt;=</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>space"</span><span class="token operator">&gt;</span><span class="token space"> </span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>REVERSE<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>string<span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">)</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>punctuation"</span><span class="token operator">&gt;</span><span class="token punctuation">;</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span><span class="token operator">&lt;</span>span<span class="token space"> </span>class<span class="token operator">=</span><span class="token string">"token<span class="token space"> </span>lf"</span><span class="token operator">&gt;</span><span class="token lf">
</span><span class="token operator">&lt;</span><span class="token operator">/</span>span<span class="token operator">&gt;</span>

Testing Use Case: Validate logic for detecting palindromic strings.

Common Scenarios for Testing String Functions

Input Validation: Verify that strings conform to specific formats, such as emails or phone numbers.
Data Transformation: Ensure proper transformations, such as concatenation or trimming, are applied.
UI Validation: Confirm that strings are displayed as required in the user interface.
Performance Testing: Validate the performance of string operations on large datasets.
Error Handling: Test how the application handles edge cases, such as empty strings or unexpected characters.

Challenges in Testing String Functions

Complex Patterns: Validating intricate patterns (e.g., regex) can be challenging.
Large Data Sets: Applying string functions on large datasets may impact performance.
Case Sensitivity: Ensuring consistency in case-sensitive environments requires careful handling.

Conclusion

String functions are essential tools for software testers working with text data in SQL. By leveraging functions like CONCAT, SUBSTRING, REPLACE, and LENGTH, testers can validate data formats, manipulate strings, and ensure consistency across the database. Mastering these functions enhances the ability to test database-driven applications effectively and ensures reliable data handling in real-world scenarios.