如何在MySQL上仅获得2个表的公共行？

Question

Probably is something simple, but, let's say I have these:

Table User (id_user, name) 
Table A (id_a, name, type, #id_user)

And then I have another one that have only its own id and the other foreign keys

Table B (id_b, #id_user1, #id_user2, #id_a, #id_Something)

So, I need a query that returns ONLY the rows of table A and table B with what they have in common. I've tried INNER JOIN but it returns all rows of Table A where the id_user from there is equal to the id_user from table B. Like, if I have these:

Table User:

id_user   name
1         Hey

Table A:

id_a   name   type   id_user
1      a      car    1
2      b      cat    1

Table B:

id_b   id_user   id_user2         id_a   id_Something
1      1         Doesn't matter   1      Doesn't matter

I need to return only the common row between Table A and Table B (that'll be something like:

id_a   name   type   id_user   id_b   id_user2
1      a      car    1         1

I've tried INNER JOIN but it returns to me everything when the id_user from A = id_user from B. I used this syntax:

SELECT     * 
FROM       B 
INNER JOIN A ON A.id_user = B.id_user;

Hope I've made myself clear, thank you a lot.

Answer 1

Is what you're going after: "Show me all the rows in A and B which share the same id_user"

SELECT User.id_user, User.name, a.id_a, b.id_b
FROM User
INNER JOIN A ON a.id_user = User.id_user
INNER JOIN B on b.id_user = User.id_user