Question

How do I perform an IF...THEN in an SQL SELECT statement?

For example:

SELECT IF(Obsolete = 'N' OR InStock = 'Y' ? 1 : 0) AS Saleable, * FROM Product 

Answer 1

The CASE statement is the closest to IF in SQL and is supported on all versions of SQL Server.

SELECT CAST(              CASE                   WHEN Obsolete = 'N' or InStock = 'Y'                      THEN 1                   ELSE 0              END AS bit) as Saleable, * FROM Product 

You only need to use the CAST operator if you want the result as a Boolean value. If you are happy with an int, this works:

SELECT CASE             WHEN Obsolete = 'N' or InStock = 'Y'                THEN 1                ELSE 0        END as Saleable, * FROM Product 

CASE statements can be embedded in other CASE statements and even included in aggregates.

SQL Server Denali (SQL Server 2012) adds the IIF statement which is also available in access (pointed out by Martin Smith):

SELECT IIF(Obsolete = 'N' or InStock = 'Y', 1, 0) as Saleable, * FROM Product