3.84
GO
CREATE VIEW IS_Student
AS
SELECT Sno,Sname,Sage
FROM Student
WHERE Sdept= 'IS';
GO
SELECT * FROM IS_Student
3.89
GO
CREATE VIEW S_G(Sno,Gavg)
AS
SELECT Sno,AVG(Grade)
FROM SC
GROUP BY Sno;
GO
SELECT * FROM S_G
3.94
SELECT *
FROM (SELECT Sno,AVG(Grade)
FROM SC
GROUP BY Sno) AS S_G(Sno,Gavg)
WHERE Gavg>=86;
【with check option】标准SQL & T-SQL
create view View_Stu_1
as
select Sno,Sname,Ssex,Sage,Sdept
from Student
where Sdept='IS'
go
create view View_Stu_2
as
select Sno,Sname,Ssex,Sage,Sdept
from Student
where Sdept='IS'
with check option;
go
insert into View_Stu_1(Sno,Sname,Ssex,Sage)--无With check option: 执行正确。 Sdept会自动补充Null。
values ('95007111','张兰11','F','19')
insert into View_Stu_2(Sno,Sname,Ssex,Sage) --有With check option: 执行错误。 没有Sdept会报错,不能够为Sdept自动补充IS。
values ('950072000','李勇00','F','19')
insert into View_Stu_2(Sno,Sname,Ssex,Sage,Sdept) --有With check option: 执行错误。有Sdept为CS,不正常执行。
values ('951000071','王1五','F2','19','CS')
insert into View_Stu_2(Sno,Sname,Ssex,Sage,Sdept) --有With check option: 执行正确。有Sdept为IS,可以正常执行。
values ('95007211','李勇11','F','19','IS')
select * from Student
select * from View_Stu_1
select * from View_Stu_2
-- 结论:
-- 标准SQL中,view 定义中有 with check option,insert 语句可以自动加条件 Sdept = IS,并最终写入表Student。
-- TSQL中,view 定义中有 with check option,insert并不能完成标准SQL的操作,执行语句会报错;仅能完成对 Sdept的 检查。
-- 也就是说,TSQL中,insert必须写Sdept。当 Sdept = IS 时,正确;Sdept = CS 时,报错。