Question

I have a table “user” with a few rows that are both foreign keys for the same table “content” kinda like this:

user.id
user.bio
user.signature

content.id
content.text

I know this is not the right way to do this from a normalization standpoint, but the “content” table is from a separate DB that I cant modify. And I dont want to duplicate the data.

Im having a problem finding a good way to join them. All I have been able to do is this, but this seems wasteful.

SELECT bio.bio, text.text
FROM(
SELECT content.text as bio
FROM content, user
WHERE user.bio = content.id
AND user.id = 4) AS bio,

SELECT content.text as content
FROM content, user
WHERE user.signature = content.id
AND user.id = 4) AS content

Answer 1

You can join one table multiple times if you give each instance a different alias:

SELECT bio.text, sig.text
FROM user u
JOIN content bio ON u.bio       = bio.id
JOIN content sig ON u.signature = sig.id
WHERE u.id = 4