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

ALTER TABLE dbo.TODA ADD [YOGUNBAKIMODASI] [BIT] NOT NULL CONSTRAINT DF_TODA_YOGUNBAKIMODASI DEFAULT 0
GO