SQL语言及关系代数解答,非常感谢!

发布网友发布时间：2022-11-26 17:58

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共3个回答

热心网友时间：2023-11-02 05:19

由于楼上的5——8写的很好了，所以我就懒省事照搬过来了

1——4题答案在图片上；

5. create view AAA as

select maker, model, speed from proct t1,PC t2 where t1.model=t2.model

union all select maker, model, speed from proct t1,Laptop t2 where t1.model=t2.model

6. with tmp as ( select model,speed from PC union all select model,speed from Laptop)

select t2.maker from tmp t1, proct t2

where t1.speed=(select max(speed) from tmp)

and t1.model=t2.model

7. update Proct set maker='A' where maker='B'

8. select avg(price) from (

select model,price from PC where speed>=150

union all select model,price from laptop where speed>=150 )

热心网友时间：2023-11-02 05:19

1-4 实在不知道如何用关系代数式表达，头一次看到有这么问的 ^_^
不知道下面的是不是你想要的
1. laptop.hd>=20
2. maker='B'
3. max(max(speed) from pc union max(speed) from laptop)
4. group by maker, having count(model)=2

5. 到底是PC机还是手提电脑？还是两者都有？下面的SQL是两者都有的情况
create view AAA as
select t1.maker, t1.model, t2.speed from proct t1,PC t2 where t1.model=t2.model
union all
select t1.maker, t1.model, t2.speed from proct t1,Laptop t2 where t1.model=t2.model

6.
with tmp as(
select model,speed from PC
union all
select model,speed from Laptop
)
select t2.maker from tmp t1, proct t2
where t1.speed=(select max(speed) from tmp)
and t1.model=t2.model

7.
update Proct set maker='A' where maker='B'

8.
select avg(price) from (
select model,price from PC where speed>=150
union all
select model,price from laptop where speed>=150
) t

热心网友时间：2023-11-02 05:20

你的题目写的也太粗糙了吧~~~哥英语不好，能不能把相应意思翻译下？？