In our Table Store_Information example,

Table Store_Information

store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego $250 Jan-07-1999
San Francisco $300 Jan-08-1999
Boston $700 Jan-08-1999

if we want to multiply the sales amount from ‘Los Angeles’ by 2 and the sales amount from ‘San Diego’ by 1.5, we key in,

SELECT store_name, CASE store_name
  WHEN ‘Los Angeles’ THEN Sales * 2
  WHEN ‘San Diego’ THEN Sales * 1.5
  ELSE Sales
  END
“New Sales”,
Date
FROM Store_Information

“New Sales” is the name given to the column with the CASE statement.

Result:

store_name New Sales Date
Los Angeles $3000 Jan-05-1999
San Diego $375 Jan-07-1999
San Francisco $300 Jan-08-1999
Boston $700 Jan-08-1999

ref: http://www.1keydata.com/sql/sql-case.html