How do I perform an IF…THEN in an SQL SELECT?

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

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

Answer 2

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 do the CAST 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

Answer 3

A new feature, IIF (that we can simply use), was added in SQL Server 2012:

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

Answer 4

case statement some what similar to if in SQL server

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

Answer 5

As an alternative solution to the CASE statement table driven approach can be used.

DECLARE @Product TABLE (ID INT, Obsolete VARCHAR(10), InStock VARCHAR(10)) 
INSERT INTO @Product VALUES
(1,'N','Y'),
(2,'A','B'),
(3,'N','B'),
(4,'A','Y')

SELECT P.* , ISNULL(Stmt.Saleable,0) Saleable
FROM 
    @Product P
    LEFT JOIN 
        ( VALUES
            ( 'N', 'Y', 1 )
        ) Stmt (Obsolete, InStock, Saleable)
        ON  P.InStock = Stmt.InStock OR P.Obsolete = Stmt.Obsolete 

Result:

ID          Obsolete   InStock    Saleable
----------- ---------- ---------- -----------
1           N          Y          1
2           A          B          0
3           N          B          1
4           A          Y          1

Answer 6

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