sqlserverでコンストレイントが存在するかどうかをどのように判断しますか?

IF  EXISTS (SELECT * FROM sys.check_constraints WHERE object_id = OBJECT_ID(N'[dbo].[CK_   ]') AND parent_object_id = OBJECT_ID(N'[dbo].[  ]'))
ALTER TABLE [dbo].[  ] DROP CONSTRAINT [CK_   ]

sqlserver            ?

 if exists(select * from sys.objects where object_id=object_id(N'  '))
 drop table