MySQL NULLIF() Function

 The NULLIF() function in MySQL is used to compare two expressions. If they are equal, the function returns NULL; otherwise, it returns the first expression.

Syntax:

NULLIF(expression1, expression2)

• expression1: The first expression to compare.
• expression2: The second expression to compare.

Description:

• If expression1 is equal to expression2, NULLIF() returns NULL.
• If expression1 is not equal to expression2, NULLIF() returns the value of expression1.

Example:

1. When values are equal:

   SELECT NULLIF(10, 10); 
   

   Output:

   NULL
   

2. When values are different:

   SELECT NULLIF(10, 20);
   

   Output:

   10
   

Use Case:

This function is often used to avoid division by zero or to handle specific conditions in queries where NULL values are needed instead of certain values.

For example, to prevent division by zero:

SELECT 100 / NULLIF(divisor, 0) AS result;

If divisor is 0, the result will be NULL instead of causing an error.