Question

I have two tables

Users: (id, name)

Relations: (user_id, relation_id)

User_id and relation_id are both ids from the table users.

What I want is ro recover all users who are friend with a specific user.

And here is my sql command: that doesn’t work:

SELECT *
FROM users
NATURAL JOIN relations
WHERE user_id IN (SELECT id FROM users WHERE name='John doe');

Could you help me?

Answer 1

SELECT users.*
FROM relations
INNER JOIN users
  ON relations.relation_id = users.id
WHERE relations.user_id = 12345;

You can also get the id with a subquery, just as you did in your example:

WHERE relations.user_id IN (SELECT id FROM users WHERE name='John doe');