Mysql 选择提供完全相同零件的成对SID的查询：

我在MySQL中有以下关系：

Suppliers(**sid**; sname; city),
Parts(**pid**; pname; color),
Catalog(**sid**; **pid**; cost),

钥匙在中间*

我想找到：

供应商对s1；s2，以便s1和s2提供完全相同的零件。 至少提供两个其他人不提供的零件的供应商。

---

1.供应商对s1；s2，以便s1和s2提供完全相同的零件：

select c1.sid,c2.sid
from catalog c1 join catalog c2 on c1.pid = c2.pid and c1.sid < c2.sid 
          and not exists 
          (
             select 1 
             from catalog c3 join catalog c4 
             on c3.sid = c1.id and c4.id = c2.sid 
                               and c3.pid <> c4.pid
          )

2.至少提供两个非其他人提供的零件的供应商

select c1.sid
from catalog c1 join catalog c2 on c1.sid = c2.sid and c1.pid < c2.pid 
          and not exists 
          (
             select 1 
             from catalog  
             where sid <> c1.sid and (pid = c1.pid or pid = c2.pid)
          )

---

我可以想象这样的事情会起作用。基本上，只要在不等于相同供应商和相同零件id的情况下进行左连接，然后查看连接数量是否等于未成功连接的行数。

非常感谢您的回复。我自己写了以下查询，但我不确定它是否正确。请让我知道。谢谢

一,

选择T1.sid，T2.sid

从T1到T2

其中选择T1.sid，C2.pid

   FROM( SELECT c1.pid

       FROM Catalog C1

       GROUP BY c1.sid) AS T1, Catalog C2

  WHERE T1.sid=c2.sid)

=

二,

选择T1.S

从T1开始

如果不存在，选择c1.sid作为S，选择c1.pid作为p1，选择C2.pid作为p2

           FROM catalog AS C1, Catalog as C2

            WHERE c1.sid=c2.sid AND

            C1.pid<>c2.pid) AS T1

        EXCEPT

        ( SELECT c3.sid AS S1, c3.pid AS p3, C4.pid AS p4

           FROM catalog AS C3, Catalog as C4

           WHERE c3.sid=c4.sid AND

            c3.pid<>c4.pid) AS T2)

不存在选择c3.sid作为S1，选择c3.pid作为p3，选择C4.pid作为p4

           FROM catalog AS C3, Catalog as C4

           WHERE c3.sid=c4.sid AND

            c3.pid<>c4.pid) AS T2)

        EXCEPT

        (SELECT c1.sid AS S, c1.pid AS p1, C2.pid AS p2

           FROM catalog AS C1, Catalog as C2

            WHERE c1.sid=c2.sid AND

            C1.pid<>c2.pid) AS T1

           FROM catalog AS C1, Catalog as C2

            WHERE c1.sid=c2.sid AND

            C1.pid<>c2.pid) AS T1

        EXCEPT

        ( SELECT c3.sid AS S1, c3.pid AS p3, C4.pid AS p4

           FROM catalog AS C3, Catalog as C4

           WHERE c3.sid=c4.sid AND

            c3.pid<>c4.pid) AS T2)

           FROM catalog AS C3, Catalog as C4

           WHERE c3.sid=c4.sid AND

            c3.pid<>c4.pid) AS T2)

        EXCEPT

        (SELECT c1.sid AS S, c1.pid AS p1, C2.pid AS p2

           FROM catalog AS C1, Catalog as C2

            WHERE c1.sid=c2.sid AND

            C1.pid<>c2.pid) AS T1