IF NOT EXISTS (SELECT * FROM SYSCOLUMNS INNER JOIN SYSOBJECTS ON SYSOBJECTS.id = SYSCOLUMNS.id 
               WHERE SYSCOLUMNS.NAME = 'EVRAKREFNO' AND SYSOBJECTS.name = 'MDLDONEMTAKIPLERI')
ALTER TABLE dbo.MDLDONEMTAKIPLERI ADD
	EVRAKREFNO nvarchar(20)
GO