[英]2 Foreign Keys referencing the same Primary Key in MySQL
like so: 像这样:
Table-student: 表 - 学生:
sID | sID | name
名称
1 -----susan 1 -----苏珊
2 -----morgan 2 -----摩根
3 -----Ian 3 -----伊恩
4 -----james 4 -----詹姆斯
Primary key = sID 主键= sID
the other table like so: 另一张表是这样的:
Table- friends 表 - 朋友
friendsID | friendsID | personA |
personA | personB
personB
1-----------1-----------3 1 ----------- ----------- 1 3
2------------1-----------2 2 ------------ ----------- 1 2
3-------------2-----------3 3 ------------- ----------- 2 3
4-------------3------------4 4 ------------- ------------ 3 4
Where Primary Key is: friendsID, personA, personB 主键是:friendsID,personA,personB
Foreign Key = personA, personB which both refer to sID in students table 外键 = personA,personB,它们都引用学生表中的sID
I want a way of querying the friends table in such a way that the personA and personB coloumn are replaced by name via sID. 我想要一种查询朋友表的方式,使得personA和personB coloumn被名称通过sID替换。 I tried natural join but it only works if there is one foreign key.
我尝试过自然连接,但只有在有一个外键时它才有效。
ie Im looking for something like this: 即我正在寻找这样的东西:
friendsID | friendsID | personA |
personA | personB
personB
1-----------Susan-----------Ian 1 ----------- -----------苏珊伊恩
2------------Sushan-----------Morgan 2 ------------ -----------苏珊摩根
3-------------morgan-----------Ian 3 ------------- -----------摩根伊恩
4-------------Ian------------james 4 ------------- ------------伊恩詹姆斯
the Natural join would work if I only had personB as a column and no personB. 如果我只将personB作为列而没有personB,那么自然联接将起作用。 For some reason the natural join is huge when I do: select*from friends NATURAL JOIN student;
出于某种原因,当我这样做时,自然联接是巨大的:从朋友中选择* NATURAL JOIN student;
Please help. 请帮忙。 Thanks
谢谢
You need to use two joins to accomplish this. 您需要使用两个连接来完成此任务。
For example: 例如:
select f.friendsID,
s1.name as personA_name,
s2.name as personB_name
from friends f
inner join student s1 on s1.sID = f.personA
inner join student s2 on s2.sID = f.personB
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