IF NOT EXISTS (SELECT * FROM SYSCOLUMNS INNER JOIN SYSOBJECTS ON SYSOBJECTS.id = SYSCOLUMNS.id 
               WHERE SYSCOLUMNS.NAME = 'ONAYLIGUNSAYISI' AND SYSOBJECTS.name = 'HTEDAVITABELADETAY')
ALTER TABLE HTEDAVITABELADETAY ADD ONAYLIGUNSAYISI INTEGER NULL
GO