Re: [HACKERS] DISTINCT ON: speak now or forever hold your peace
От | Peter Eisentraut |
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Тема | Re: [HACKERS] DISTINCT ON: speak now or forever hold your peace |
Дата | |
Msg-id | Pine.LNX.4.21.0001260143120.9535-100000@localhost.localdomain обсуждение исходный текст |
Ответ на | DISTINCT ON: speak now or forever hold your peace (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: [HACKERS] DISTINCT ON: speak now or forever hold your peace
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Список | pgsql-sql |
On 2000-01-24, Tom Lane mentioned: > If I don't hear loud hollers very soon, I'm going to eliminate the > DISTINCT ON "feature" for 7.0. As previously discussed, this feature > is not standard SQL and has no clear semantic interpretation. Our documents say that DISTINCT ON is equivalent to GROUP BY. I still don't see why that wouldn't be true. You can always rewrite select distinct on a a,b from test as select a, xxx(b) from test group by a where xxx is some aggregate function (presumably min or max). You can also rewrite select distinct on a a,b,c from test as select a, b, c from test group by a, b, c or using some aggregates here as well. At least you can control your results that way. -- Peter Eisentraut Sernanders väg 10:115 peter_e@gmx.net 75262 Uppsala http://yi.org/peter-e/ Sweden
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