left join Opcje

[deniol13]

witam, mam takie zapytanie

[SQL] pobierz, plaintext 
SELECT f.*, t.* FROM forums f
LEFT JOIN topics t 
WHERE f.forum_id = t.forum_id
ORDER BY t.topic_start_date DESC
LIMIT 0, 1
[SQL] pobierz, plaintext 

efekt w pma
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE f.forum_id = t.forum_id
ORDER BY t.topic_start_date DESC
LIMIT 0, 1' at line 3

[Mchl]

LEFT (RIGHT) JOIN wymaga warunku złączenia w ON

Kod

SELECT f.*, t.* FROM forums f
LEFT JOIN topics t
ON f.forum_id = t.forum_id
ORDER BY t.topic_start_date DESC
LIMIT 0, 1

[deniol13]

a jak moge ograniczyc ilosc joinow ?
bo chce by mi pobralo forum i do kazdego forum ostatni temat ale jak mam dwa tematy w forum to pobiera mi forum x2 a nie dam LIMIT 0,1 (usunalem z wczesniejszego sql) bo mam kilka for

[Mchl]

Kod

SELECT f.*, t.* FROM forums f
LEFT JOIN (
  SELECT * FROM topics AS t
  CROSS JOIN (
    SELECT forum_id, MAX(topic_start_date) AS topic_start_date
    FROM topics
    GROUP BY forum_id
  ) ON (forum_id, topic_start_date)
) AS t
ON f.forum_id = t.forum_id
ORDER BY t.topic_start_date DESC
LIMIT 0, 1