我有以下表格:
Suppliers(Sno, Sname, Address)
Parts(Pno, Pname, Colour)
Catalogue(Sno, Pno, Price)
我想找到供应每个零件的供应商的Sno。
到目前为止,我已经写了这个:
SELECT s.sname
FROM suppliers s JOIN catalogue c
USING s.sno
现在我该如何写"供应每个零件的供应商"?
我正在考虑为每个供应商 Sno 提供零件 = 计数(pno) 的计数(*)。有人可以给我一个提示/写下平等的第一部分吗?
谢谢!
SELECT s.sname
FROM suppliers s
INNER JOIN catalogue c
ON s.Sno = c.Sno
GROUP BY s.sname
HAVING COUNT(c.Pno) = (SELECT COUNT(Pno) FROM Parts)
你很接近。您需要添加一个带有子查询的 group by/having 子句:
group by s.sname having count(*) = (select count(*) from catalogue)
在我的头顶上,你可以写
SELECT s.Sno
FROM suppliers s
WHERE NOT EXISTS (
SELECT p.Pno
FROM parts p
WHERE NOT EXISTS (
SELECT c.*
FROM catalogue c
WHERE c.Pno = P.Pno
AND c.Sno = S.Sno
)
)
即不存在的供应商(我们不提供的部分),用于避免计数的解决方案。不知道这是否比计数更有效或更差。
SELECT s.Sno, s.Sname
FROM Suppliers s
CROSS JOIN Parts p
LEFT JOIN Catalogue c ON s.Sno = c.Sno AND p.Pno = c.Pno
GROUP BY s.Sno, s.Sname
HAVING COUNT(*) = COUNT(c.Pno)
试试这个:
alter proc clr
@c char(10),
@pno int output
as
begin
declare @f int
if exists(select p# from p where colour=@c)
begin
select @pno=p# from p where colour=@c
--set @f=1
end
-- else
-- set @f=0
-- return @f
end
--clr 'red',2
select p# from p where colour='red'
alter proc prcs
@c char(20)
as
begin
declare @pno numeric(2)
declare @f int
exec @f=clr @c,@pno output
--if @f=1
-- begin
select @pno
select s# from sp where p#=@pno
--set @i=1
-- end
--set @i=0
--return @i
end
prcs 'red'
select * from sp
select * from p,sp where p.p#=sp.p# and colour='red'
alter proc prcj
@c char(10)
as
begin
declare @i int
exec @i=prcs @c
if @i=1
begin
print'list of supplier'
select sname from s
where s#=@c
end
else
print'this record is not found'
end