## How to Use the MySQL NULLIFF() Function

In this tutorial, you'll learn how to use the **MySQL NULLIF()** function. **NULLIF** is a function to compare two expressions and return NULL if they are equal. Otherwise, it returns the first expression.

### MySQL NULLIF() Syntax

The syntax of the **NULLIF**() function is as follow:

NULLIF(expression_1, expression_2)

### NULLIF Examples

#### Example 1

The following statement compares two integers and returns as * Message*:

SELECT NULLIF(1, 2) AS Message;

Since integer 1 is not equal to 2, **NULLIF()** returns 1, which is the first expression.

#### Example 2

The following statement returns **NULL** because both expressions in the **NULLIF()** function are equal.

SELECT

NULLIF("Apple", "Apple") AS Message;

#### Example 3

The following statement returns NULL, because both expressions are equal.

SELECT

NULLIF("The tutorial of NULLIF function.", "THE TUTORIAL of NULLIF Function.")ASMessage;

As you can see, both expressions are not the same if you consider the lowercase and uppercase characters are different. Since **NULLIF** is case-insensitive, the lowercase and uppercase characters treated the same.

#### Example 4

The following illustrates an example of using **SUM**() function inside **NULLIF**():

SELECT

NULLIF(SUM(1+2), 2) AS Message;

The statement returns 3. The integer 3 is the returned value of **SUM**(1+2), greater than 2.

In this tutorial, you've learned how to use the **MySQL NULLIF** function. **NULLIF** is used to return the **NULL **value if both expressions are equal. Otherwise, it returns the first expression.