sql語句關系代數練習
對於表結構：
product(maker,model,type)
maker:表示生產廠商
model：生產的產品型號
type：產品類型，有pc laptop printer三種
pc(model,speed,ram,hd,price)
表示型號，速度，內存大小，硬盤大小，價格
laptop(model,speed,ram,hd,screen,price)
表示型號，速度，內存大小，硬盤大小，屏幕大小和價格
printer（model,color,type,price)
model：打印機型號；
color：是否彩色， T 彩色，F 黑白
type:類型，ink-jet 表示噴墨， laser 表示激光；
price：單價
這是一套難度大得不溜秋的題嚶嚶嚶，本人水平有限，對語句的理解還不夠深，語句不一定都是最優解，有的題目有多種解，如有疑問錯誤歡迎指出~
查詢生產pc也生產laptop的廠商
select product.maker
from product
join laptop
on product.model = laptop.model
intersect
select product.maker
from product
join pc
on product.model = pc.model
查詢生產型號為2001的廠商信息及該型號所屬產品的種類
select maker,type from product where model='2001'
查詢廠商A 生產的PC中price大於900的產品型號
select product.model
from product
inner join pc
on product.model=pc.model
where pc.price>900 and product.maker='A'
查詢廠商B生產的所有產品的型號和價格
select product.maker,printer.price
from product
inner join printer
on product.model = printer.model
where printer.type = 'ink-jet'
分類統計廠商（maker）A生產的各種產品的數量
select type,count(model) from product where maker='A' group by type
查詢所有彩色激光打印機的生產商及型號
select a.maker,a.model
from product a
inner join printer b
on a.model = b.model
where b.color = 'T' and b.type = 'laser'
找出生產產品型號最多的廠商
select top 1 maker from product group by maker order by count(*) desc
查詢出哪個生產廠商的筆記本電腦的硬盤容量至少100G
select a.maker
from product a
inner join laptop b
on a.model = b.model
group by a.maker
having min(b.hd)>=100
找出那些既出售筆記本電腦又出售PC的廠商
select product.maker
from product
inner join pc
on product.model = pc.model
group by product.maker
intersect
select product.maker
from product
inner join laptop
on product.model = laptop.model
查詢具有同樣處理速度和同樣內存大小的PC對
顯示滿足條件的pc對的型號,同樣的pc對只出現1次，如001 與 002 符合條件， 則僅出現001 002，不出現002 001
select a.model,b.model
from pc a,pc b
where a.speed=b.speed and a.ram=b.ram and a.model<>b.model and a.model<b.model
查詢至少生產三種不同處理速度電腦（含pc和laptop）的廠商
select maker from
(
select maker, product.model, speed from
product join pc on product.model = pc.model
union
select maker, product.model, speed from
product join laptop on product.model = laptop.model
) as a
group by maker
having count(distinct speed) >= 3;
統計出pc，laptop，printer三種產品的不同型號數量，並按數量從大到小排序
select type, count(model) as c from
(
select type, product.model as model from
product join pc on product.model = pc.model
union
select type, product.model as model
from product join laptop on product.model = laptop.model
union
select product.type, product.model as model
from product join printer on product.model = printer.model
) as a
group by type
order by c desc;
有客戶有1500元錢，買laptop或pc，要求硬盤容量不小於80，請給出可能的產品型號，生產廠商
select product.maker,product.model from product
inner join laptop on product.model = laptop.model where laptop.hd >=80 and laptop.price <=1500
union
select product.maker,product.model from product
inner join pc on product.model = pc.model where pc.hd >=80 and pc.price <=1500
找出至少生產5種不同型號產品的廠商
select maker from product
group by maker
having count(*)>=5
完成功能使得：廠商A的產品升級，所有pc速度提高100，硬盤容量增加50，價格上調300
Update pc SET pc.speed = pc.speed +100,pc.hd=pc.hd+50,pc.price=pc.price+300
FROM product INNER JOIN pc ON product.model=pc.model
where product.maker='A'
完成功能：廠商E新增一種pc產品，型號1090，速度200，內存128，硬盤160，價格800
insert into pc values ("1090",200,128,160,800);
insert into product values ("E","1090","pc");
完成功能：廠商C生產的laptop，型號2013停產，需要從相關關系種去除
delete a
from product a
inner join laptop b
on a.model = b.model
where a.maker='C' and a.model = '2013'
完成功能：廠商A生產的產品1001型號變更為1091，其余信息不變
Update b SET b.model = '1091'
FROM product a INNER JOIN pc b
ON a.model=b.model
where a.maker='A' and b.model = '1001';
Update a SET a.model = '1091'
FROM product a
where a.model = '1001';
廠商H破產，所有其生產的產品需移除
delete b from product a inner join pc b
on a.model = b.model
where a.maker = 'H';
delete b from product a inner join laptop b
on a.model = b.model
where a.maker = 'H';
delete b from product a inner join printer b
on a.model = b.model
where a.maker = 'H';
delete a from product a
where a.maker ='H';