Question

Is it possible to have a conditional join based on parameter; for example:

//PSEUDE CODE:
DECLARE @condition bit
SET @condition=1 or 0 

SELECT * 
FROM tableA 
INNER JOIN tableB on tableA.SomeColumn = tableB.SomeColumn 
if @condition = 0 THEN 
   INNER JOIN tableC ON tableC.SomeCOlumn = TableA.SomeColumn 
ELSE
   INNER JOIN tableD ON tableD.SomeColumn=TableA.someColumn

Thank you

Answer 1

Description

You can build a varchar containing your query and use exec to execute them.

Executes a command string or character string within a Transact-SQL batch, or one of the following modules: system stored procedure, user-defined stored procedure, CLR stored procedure, scalar-valued user-defined function, or extended stored procedure.

Sample

DECLARE @SQL varchar(max)
DECLARE @condition bit
SET @condition=1 

SET @SQL = 'SELECT * FROM tableA INNER JOIN tableB on tableA.SomeColumn=tableB.SomeColumn'

IF (@condition = 1) 
BEGIN 
    SET @SQL = @SQL + ' INNER JOIN tableC ON tableC.SomeCOlumn=TableA.SomeColumn'
END ELSE BEGIN
    SET @SQL = @SQL + ' INNER JOIN tableD ON tableD.SomeColumn=TableA.someColumn'
    END

exec(@SQL)

More Information

• MSDN – EXECUTE (Transact-SQL)