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

ALTER TABLE dbo.HAMELIYAT ADD 	[HABLOKAXAILLER] [BIT] NOT NULL CONSTRAINT DF_HAMELIYAT_HABLOKAXAILLER DEFAULT 0
GO