MySQL CASE Function

Example

Go through conditions and return a value when the first condition is met:

SELECT OrderID, Quantity,
CASE
    WHEN Quantity > 30 THEN "The quantity is greater than 30"
    WHEN Quantity = 30 THEN "The quantity is 30"
    ELSE "The quantity is under 30"
END
FROM OrderDetails;

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Definition and Usage

The CASE statement goes through conditions and return a value when the first condition is met (like an IF-THEN-ELSE statement). So, once a condition is true, it will stop reading and return the result.

If no conditions are true, it will return the value in the ELSE clause.

If there is no ELSE part and no conditions are true, it returns NULL.

Syntax

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    WHEN conditionN THEN resultN
    ELSE result
END;

Parameter Values

Parameter	Description
condition1, condition2, ...conditionN	Required. The conditions. These are evaluated in the same order as they are listed
result1, result2, ...resultN	Required. The value to return once a condition is true

Technical Details

Works in:	From MySQL 4.0

More Examples

The following SQL will order the customers by City. However, if City is NULL, then order by Country:

Example

SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);

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