# **NULLIF**

## **Grammar Description**

The `NULLIF()` function is used to compare the values of two expressions. If the values of `expr1` and `expr2` are equal, the `NULLIF()` function returns `NULL`; otherwise, the value of `expr1` is returned. This function is usually used to deal with avoiding division by zero or avoiding errors when using invalid values in calculations.

## **Grammar Structure**

```text
> NULLIF(expr1,expr2)
```

## **Example**

```text
CREATE TABLE employees ( id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(50) NOT NULL, salary DECIMAL(10, 2) );

INSERT INTO employees (name, salary) VALUES ('John Doe', 1000), ('Alice Smith', 2000), ('Bob Johnson', 1500);

-- Use the NULLIF() function to set the salary of an employee whose salary is a specific value to NULL. The NULLIF(salary, 1500) function compares the value of the salary field to 1500. If the value of salary is equal to 1500, NULL is returned, otherwise the value of salary is returned.
mysql> SELECT name, salary, NULLIF(salary, 1500) AS adjusted_salary FROM employees;
+------------------------------------------------------------------------------------------------------------------------------
| name | salary | adjusted_salary |
+------------------------------------------------------------------------------------------------------------------------------
| John Doe | 1000.00 | 1000.00 |
| Alice Smith | 2000.00 | 2000.00 |
| Bob Johnson | 1500.00 | |
+------------------------------------------------------------------------------------------------------------------------------
3 rows in set (0.01 sec)
```