Question

I have 2 tables: edges and users

edges (with constraint: id1 < id2):

id1
name1
id2
name2

users:

id
name

I’d like to get a result set of only edges (id1, name1, id2, name2) such that BOTH id1 and id2 are in the users table. This seems pretty simple, but I’m having trouble getting it. My attempt:

SELECT
   e.id1 AS id1,
   e.name1 AS name1,
   e.id2 AS id2,
   e.name2 AS name2
FROM 
   edges AS e,
   users AS u
WHERE u.id = e.id1

UNION

SELECT
   e.id1 AS id1,
   e.name1 AS name1,
   e.id2 AS id2,
   e.name2 AS name2
FROM 
   edges AS e,
   users AS u
WHERE u.id = e.id2

Any pointers?

Answer 1

Try using two INNER JOINS like this:

SELECT * FROM edges e 
JOIN users u1 ON e.name1 = u1.name 
JOIN users u2 ON e.name2 = u2.name