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IS NULL (Transact-SQL)

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric SQL database in Microsoft Fabric

Determines whether a specified expression is NULL.

Transact-SQL syntax conventions

Syntax

expression IS [ NOT ] NULL

Arguments

expression

Any valid expression.

  • NOT

    Specifies that the Boolean result is negated. The predicate reverses its return values, returning TRUE if the value isn't NULL, and FALSE if the value is NULL.

Return types

Boolean

Return code values

If the value of expression is NULL, IS NULL returns TRUE; otherwise, it returns FALSE.

If the value of expression is NULL, IS NOT NULL returns FALSE; otherwise, it returns TRUE.

Remarks

To determine whether an expression is NULL, use IS NULL or IS NOT NULL instead of comparison operators (such as = or !=). Comparison operators return UNKNOWN when either or both arguments are NULL.

Examples

The code samples in this article use the AdventureWorks2022 or AdventureWorksDW2022 sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.

A. Return the name and weight for all products

The following example returns the name and the weight for all products for which either the weight is less than 10 pounds, or the color is unknown, or NULL.

SELECT Name,
       Weight,
       Color
FROM Production.Product
WHERE Weight < 10.00
      OR Color IS NULL
ORDER BY Name;
GO

Examples: Azure Synapse Analytics and Analytics Platform System (PDW)

B. Return the full names of all employees with initials

The following example returns the full names of all employees with middle initials.

SELECT FirstName,
       LastName,
       MiddleName
FROM DIMEmployee
WHERE MiddleName IS NOT NULL
ORDER BY LastName DESC;

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