如果存在这个表，则删除这个表的各种sql写法

drop table if exists address_book

IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[表名]') AND type in (N'U'))
DROP TABLE [dbo].[表名]

IF  EXISTS (SELECT * FROM sysobjects WHERE object_id = OBJECT_ID(N'[dbo].[表名]') AND type in (N'U')) DROP TABLE [dbo].[表名]