mysql-5.0.41 moved back to ready

[Radoslaw Zielinski]

Elan Ruusamäe <glen at delfi.ee> [25-05-2007 16:23]:
[...]
> mysql> select a.category_id,count(*) from album a where exists (select album_id from image where album_id=a.id) group by 1;
> Empty set (0.00 sec)

This query makes little sense and is not ANSI SQL compliant (category_id
not used in aggregate statement or GROUP BY), so both behaviours are
incorrect -- it should return an error.

If you want to count the number of albums in a given category which have
images, that would be the proper query (exists vs join: depending on the
amount of data):

  select a.category_id, count(*)
    from album a
    join image i on i.album_id=a.id
    group by a.category_id;


</offtopic>

-- 
Radosław Zieliński <radek at pld-linux.org>
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