SQL CASE Keyword
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:
WHEN Quantity > 30 THEN 'The quantity is greater than 30'
WHEN Quantity = 30 THEN 'The quantity is 30'
ELSE 'The quantity is under 30'
The following SQL will order the customers by City. However, if City is NULL, then order by Country:
WHEN City IS NULL THEN Country