Como adicionar coluna dinâmica a uma tabela existente

CREATE PROC ADD_CHECK
AS 
BEGIN
    DECLARE @COLUMN VARCHAR(50)
    DECLARE @QUERY VARCHAR(255)
    DECLARE @QUERY1 VARCHAR(255)

    SET @COLUMN= (SELECT TOP 1 NAME FROM TABLE1 WHERE ID=(SELECT MAX (ID)     FROM TABLE1))

    IF EXISTS(SELECT 1 FROM TABLE1 WHERE [email protected]) 
    BEGIN
        SET @QUERY = 'ALTER TABLE TABLE2 ADD ' + @COLUMN + ' VARCHAR (50)'
        SET @QUERY1 = 'ALTER TABLE TABLE2 ADD ' + @COLUMN + '_COMPLETEDDATE VARCHAR     (50)'
        EXEC(@QUERY)
    END
END