IF NOT EXISTS (SELECT * FROM SYSCOLUMNS INNER JOIN SYSOBJECTS ON SYSOBJECTS.id = SYSCOLUMNS.id 
              WHERE SYSCOLUMNS.NAME = 'AOA15' AND SYSOBJECTS.name = 'HAMELIYATPREOPERATIF')
ALTER TABLE dbo.[HAMELIYATPREOPERATIF] ADD AOA15 bit NOT NULL CONSTRAINT [DF_HAMELIYATPREOPERATIF_AOA15] DEFAULT (0)
GO