SQL CASE Expression
The SQL CASE Expression
CASE expression goes through conditions and returns 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 returns
the value in the
If there is no
ELSE part and no conditions are true, it returns NULL.
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
Below is a selection from the "OrderDetails" table in the Northwind sample database:
SQL CASE Examples
The following SQL goes through conditions and returns a value when the first condition is met:
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 AS QuantityText
The following SQL will order the customers by City. However, if City is NULL, then order by Country:
WHEN City IS NULL THEN Country