刚学数据库,求指导下面几个语句的含义,写上注释。谢谢了
if exists(select * from sysobjects where id=object_id(N'Test1')
and OBJECTPROPERTY(id, N'IsUserTable') = 1)
if exists(select * from sysobjects where id=object_id(N'Test1')
and OBJECTPROPERTY(id, N'IsUserTable') = 1)
if exists(select * from sysobjects where id=object_id(N'Test1')
and OBJECTPROPERTY(id, N'IsUserTable') = 1)
--你这个不全,应该还有一句
drop table Test1
如果数据库中存在用户创建的表Test1就删除Test1
and OBJECTPROPERTY(id, N'IsUserTable') = 1)--表示在数据库中存在TEST1的表 IsUserTable=1表示这个表还是用户表,而不是系统表
---建表语句
if object_id('Test1') is not null
drop table Test1
go
create table Test1(
id int identity(1,1) primary key,
startTime datetime,
endTime datetime,
人员 nvarchar(5))
and OBJECTPROPERTY(id, N'IsUserTable') = 1)exists是判断子查询是否返回记录子查中的select * from sysobjects where id=object_id(N'Test1')
and OBJECTPROPERTY(id, N'IsUserTable') = 1
查找到id和表属性是用户表的记录