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SQL NULLIF Function

Quick summary: The SQL NULLIF() function returns NULL if two expressions are equal.

SQL NULLIF Syntax 

NULLIF(expression1, expression2)
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SQL NULLIF Basic examples 

SELECT NULLIF(0, 0);
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Output:
NULL

Returns NULL when values match.

SQL NULLIF Real-world usage 

SELECT total / NULLIF(quantity, 0) FROM orders;
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Output:
Safe division

Prevents division by zero.

SQL NULLIF Edge cases 

SELECT NULLIF(5, 3);
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Output:
5

Returns first value when not equal.

SQL NULLIF Common mistakes

Confusing NULLIF with COALESCE

They solve opposite problems.

Incorrect
COALESCE(a, b)
Correct
NULLIF(a, b)

Use NULLIF to nullify values.

SQL NULLIF Frequently Asked Questions

What does NULLIF() do in SQL?

Returns NULL if two expressions are equal.

Use case of NULLIF()?

Avoid division by zero.

Syntax?

NULLIF(value1, value2).

Return type?

Same as first argument.

Common mistake?

Expecting boolean result.

Performance?

Fast.

Alternative?

CASE.

Used in calculations?

Yes.

Handles NULL?

Yes.

Used with COALESCE?

Yes.

Best practice?

Use for safe math.

Used in reports?

Yes.

SQL NULLIF Related SQL Keywords