Nepochopeny GROUP BY

Blackshadow · Napísal **Blackshadow**: 20.02.2010 15:44 | Nepochopeny GROUP BY

Zdravim,
mam SQL prikaz:

Kód:

SELECT post_time, topic_id FROM forum_posts WHERE forum_id=16 ORDER BY post_time DESC LIMIT 10

vypise:

Kód:

topic_id - post_time
- 1266676207
- 1266675998
- 1266675993
- 1266664388
- 1266532737
- 1266530089
- 1265731400
- 1265731023
- 1265729631
- 126221649

ja by som ale potreboval, aby tie topic_id vzdy zobral iba raz a posledny prispevok z nich, tak som pouzil:

Kód:

SELECT post_time, topic_id FROM forum_posts WHERE forum_id=16 GROUP BY topic_id ORDER BY post_time DESC LIMIT 10

vypise ale:

Kód:

topic_id - post_time
- 1265731400
- 1262216490
- 1257801084
- 1257801032
- 1257800886
- 1257800636
- 1255440964
- 1254748323
- 1253968841
- 1251811044

Co to je ?

kde je 944 ?

p360t · Napísal **p360t**: 20.02.2010 15:59 | Nepochopeny GROUP BY

Skús

Kód:

SELECT MAX(post_time), topic_id FROM forum_posts WHERE forum_id=16 GROUP BY topic_id ORDER BY post_time DESC LIMIT 10

Keď používaš GROUP BY, mal by si selectovať len agregované alebo zgrupované stĺpce (tj. len tie, na ktoré je použitá nejaká MAX, MIN, COUNT, AVG funkcia a tie ktoré sú vymenované v GROUP BY).

Blackshadow · Napísal autor témy **Blackshadow**: 20.02.2010 16:32 | Nepochopeny GROUP BY

Vypise:

Kód:

- 
- 
- 
- 
- 
- 
- 
- 
- 
- 

Takze to nespravilo spravne a este aj post_time zmizol

EDIT:

Kód:

SELECT MAX(post_time) as post_time, topic_id FROM forum_posts WHERE forum_id=16 GROUP BY topic_id ORDER BY post_time DESC LIMIT 10

a ide

Nepochopeny GROUP BY

Nepochopeny GROUP BY

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