if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[采购订单_供货商_fk]') and OBJECTPROPERTY(id, N'IsForeignKey') = 1)
ALTER TABLE [dbo].[采购订单] DROP CONSTRAINT 采购订单_供货商_fk
GO
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[采购订单历史_供货商_fk]') ...
