Question

Given a user name in a Drupal 7.17 database using PostgreSQL 8.4.13 I am trying to fetch user info (uid, city, gender, avatar) distributed over several tables.

The avatar (the f.filename below) is however optional – some users don’t have it.

For users, that do have avatars my query works well:

#  select
        u.uid,
        /* u.pass, */
        f.filename,
        g.field_gender_value,
        c.field_city_value
from
        drupal_users u,
        drupal_file_managed f,
        drupal_field_data_field_gender g,
        drupal_field_data_field_city c
where
        u.name='Alex' and
        u.picture=f.fid and
        g.entity_id=u.uid and
        c.entity_id=u.uid
;
 uid |         filename         | field_gender_value | field_city_value
-----+--------------------------+--------------------+------------------
   1 | picture-1-1312223092.jpg | Male               | Bochum
(1 row)

However for users, who don’t have avatar I get empty result.

When I omit the drupal_file_managed f table – it works again:

#  select
        u.uid,
        /* u.pass, */

        g.field_gender_value,
        c.field_city_value
from
        drupal_users u,

        drupal_field_data_field_gender g,
        drupal_field_data_field_city c
where
        u.name='mvp' and

        g.entity_id=u.uid and
        c.entity_id=u.uid
;
  uid  | field_gender_value | field_city_value
-------+--------------------+------------------
 18539 | Male               | Moscow
(1 row)

How could I modify my join statement to ensure that it always returns 1 row for valid users – regardless if they have avatar or not? The f.filename column can be null for the latter cases.

Do I want a left outer join here? (I’m afraid it will return several rows instead of 1).

Answer 1

With COALESCE() you can even plug in a default value, if the filename appears to be missing:

SELECT u.uid AS uid
        , COALESCE(f.filename, 'goatsex.jpg') AS filename
        , g.field_gender_value AS gender_value
        , c.field_city_value AS city_value
FROM drupal_users u
JOIN drupal_field_data_field_gender g ON g.entity_id=u.uid 
JOIN drupal_field_data_field_city c ON c.entity_id=u.uid
LEFT JOIN drupal_file_managed f ON u.picture=f.fid 
WHERE u.name='Alex' 
        ;