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NULLIF function
In SQL, the NULLIF function is used to replace an expression with NULL if expression matches a specified value.
The syntax of the NULLIF function generally looks like this :
NULLIF(expression1, expression2)
• Define the 'expression1/value1' to be evaluated for a match.
• Specify the 'expression2/value2' to return as null if it matches with the expression.
Here, If the expression1 equals the expression2, NULL is returned; otherwise, the expression is returned as is.
Here's an example of how you might use the NULLIF function :
1. Let's assume we have a table named "[Employees]".
2. Let's assume you want to replace the value 'Female' in the Gender column with NULL.
3. Run below SQL statement :
SELECT *, NULLIF(Gender, 'Female') AS [Gender2]
FROM [Employees];
4. In the above statement, the NULLIF function substitutes all occurrences of 'Female' within the Gender column with NULL.
Remember :
Using this function in a select statement won't modify the [Employees] table directly, but it will only be reflected in the select statement's output.