SQL Server IS NOT NULL Operator

The IS NOT NULL operator in SQL Server is used to filter the result set and retrieve rows where a specified column does not contain a NULL value. It is the negation of the IS NULL operator and is commonly used in the WHERE clause to identify records with known or specified data. This guide will cover the syntax, examples, output, explanations, use cases, important points, and a summary of using the IS NOT NULL operator in SQL Server.

Syntax

SELECT column1, column2, ...
FROM table_name
WHERE column_name IS NOT NULL;

Example

Consider a table named employees with a column named email. We want to retrieve employee records where the email address is specified and not NULL.

SELECT employee_id, employee_name
FROM employees
WHERE email IS NOT NULL;

Output

The output will display the details of employees whose email address is not NULL.

| employee_id | employee_name |
|-------------|----------------|
| 101         | John           |
| 102         | Bob            |
| 103         | Alice          |

Explanation

• The IS NOT NULL operator is used to filter rows where the email column does not contain a NULL value.
• The result set includes employees for whom the email address is specified.

Use

The IS NOT NULL operator in SQL Server is used for:

• Identifying records with known or specified data in a specific column.
• Filtering out records with missing or unknown data.
• Writing queries to retrieve or update records based on the presence of a particular value.

Important Points

• The IS NOT NULL operator checks whether a column or expression is not NULL.
• It is crucial to handle NULL and NOT NULL values appropriately in SQL queries.

Summary

The IS NOT NULL operator in SQL Server is a useful tool for filtering records with known or specified data. It complements the IS NULL operator and is commonly employed when querying for records where a particular column has been assigned a value. Understanding how to use the IS NOT NULL operator is essential for building robust and accurate SQL queries in SQL Server databases.