Case
The CASE command is used is to create different output based on conditions.
The following SQL goes through several conditions and returns a value when the specified condition is met:
Example
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;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);