SQL Server ISNULL() Function

Syntax

ISNULL(value, replacement)

Basic Example

SELECT ISNULL(phone, 'No phone') AS phone_display
FROM customers;

When to use it

Use ISNULL when you need a null operation in SQL Server. This page is designed as a quick reference for developers, analysts, and students comparing SQL dialects.

Common mistake

A common mistake is copying syntax from another SQL dialect. Always verify function name, argument order, and formatting tokens for SQL Server.

Related SQL Functions

• MySQL IFNULL() Function
• MySQL COALESCE() Function
• MySQL NULLIF() Function
• PostgreSQL COALESCE() Function
• PostgreSQL NULLIF() Function
• SQL Server CONCAT() Function

FAQ

Is ISNULL available in every SQL database?

Not always. Function names and argument behavior can differ across SQL engines.

Can I use this in SELECT queries?

Yes. Most SQL functions are commonly used in SELECT and often in WHERE, ORDER BY, and GROUP BY depending on the function.