SQL Server ISNULL() Function

The ISNULL() function in SQL Server provides a way to handle potential NULL values in your data. It allows you to replace NULL values with a specified value, making your data cleaner and easier to work with.

ISNULL(): Definition and Usage

NULL values can sometimes cause issues in your queries or applications. ISNULL() solves this by letting you substitute a NULL with a value you choose. If the expression isn't NULL, the function simply returns the expression's original value.

Syntax


ISNULL(expression, value)

Parameter Values

Parameter	Description
`expression`	The expression you are checking for `NULL`. This is required.
`value`	The value to return if the `expression` is `NULL`. This is required.

Examples

Replacing a NULL Value

This example replaces a NULL with the string 'W3Schools.com'.

Syntax


SELECT ISNULL(NULL, 'W3Schools.com');

Output


W3Schools.com

Handling a Non-NULL Value

If the expression isn't NULL, the original value is returned.

Syntax


SELECT ISNULL('Hello', 'W3Schools.com');

Output


Hello

Replacing NULL with a Number

Replacing a NULL with a numeric value.

Syntax


SELECT ISNULL(NULL, 500);