Question

I know there’s got to be a way to do this, but for the life of me I can’t figure it out:

I have 3 tables I want to join together (simplified to illustrate):

users
uid mail
1   [e-mail]
2   [e-mail]
3   [e-mail]

profile_fields
fid name        label
1   full_name   Full Name
2   phone       Phone

profile_values
uid fid value
1   1   Q Q
1   2   5555555555
2   1   Ww Ww
3   2   4444525411

I’d like to get results of the form:

uid mail        full_name   phone
1   [e-mail]   Q Q     5555555555
2   [e-mail]   Ww Ww       NULL
3   [e-mail]   NULL        44445454111

I’ve tried various SELECTs with different JOIN conditions but I can’t seem to figure out how to get the rows of profile_fields to be my columns in my SELECT

EDIT: I’ve also tried googling around, but I can’t seem to figure out how to phrase this to google.

Answer 1

Use:

SELECT u.uid,
       u.mail,
       MAX(CASE WHEN pf.name = 'full_name' THEN pv.value END) AS full_name,
       MAX(CASE WHEN pf.name = 'phone' THEN pv.value END) AS phone
  FROM USERS u
  LEFT JOIN PROFILE_VALUES pv ON pv.uid = u.uid
  JOIN PROFILE_FIELDS pf ON pf.fid = pv.fid
                        AND pf.name IN ('full_name', 'phone')
GROUP BY u.uid, u.mail