Question

While I was working on a small task I came across a situation

DECLARE   @i  INT ,
    @l  INT ,
    @desc  CHAR(50)

SET    @l = 1 
SET    @i = 20
WHILE   ( @l <= @i ) 
BEGIN
  SELECT  'Test'   AS   'Test'+@l
  SET @l =   @l  +  1
END

In this code I want when a loop run all time column name changed with the value of @l.

Answer 1

You need to build the statement dynamically and use EXECUTE or sp_executesql to execute the statement.

DECLARE   @i  INT ,
          @l  INT ,
          @desc  CHAR(50)

SET @l = 1 
SET @i = 20

WHILE   ( @l <= @i ) 
BEGIN
    EXEC ('SELECT  ''Test''   AS   Test'+@l)
    SET @l =   @l  +  1
END

Recomended reading when entering the world of dynamic SQL :The Curse and Blessings of Dynamic SQL

Using sp_executesql instead:

DECLARE   @i  INT ,
          @l  INT ,
          @desc  CHAR(50),
          @SQL NVARCHAR(100)

SET @l = 1 
SET @i = 20

WHILE   ( @l <= @i ) 
BEGIN
    SET @SQL = N'SELECT  ''Test''   AS   Test'+CAST(@l AS NVARCHAR(10))
    EXEC sp_executesql @SQL
    SET @l =   @l  +  1
END