IS NULL

What is IS NULL?

In SQL, IS NULL is used to check whether a column has a NULL value. A NULL represents missing or unknown data, not zero or an empty string.

2. Syntax

SELECT column1, column2
FROM table_name
WHERE column_name IS NULL;

• column_name – The column you want to check for NULL values.
• table_name – The table containing the column.

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3. Example

Suppose you have a table called Employees:

EmployeeID	Name	Department
1	Alice	HR
2	Bob	NULL
3	Charlie	IT
4	David	NULL

To find all employees without a department:

SELECT Name
FROM Employees
WHERE Department IS NULL;

Result:

Name
Bob
David

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4. Using IS NOT NULL

To find rows where a column does have a value, use IS NOT NULL:

SELECT Name
FROM Employees
WHERE Department IS NOT NULL;

Result:

Name
Alice
Charlie

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5. Key Points

• IS NULL is used for filtering missing data.
• NULL is not the same as zero or empty string.
• Always use IS NULL or IS NOT NULL – do not use = or != with NULL.