IF NOT EXISTS (SELECT * FROM SYSCOLUMNS INNER JOIN SYSOBJECTS ON SYSOBJECTS.id = SYSCOLUMNS.id 
            WHERE SYSCOLUMNS.NAME = 'IHASTALIKACIKLAMA' AND SYSOBJECTS.name = 'HYATISDUSME')

ALTER TABLE HYATISDUSME ADD IHASTALIKACIKLAMA NVARCHAR(150) NULL