Re: a wierd query
От | Stephan Szabo |
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Тема | Re: a wierd query |
Дата | |
Msg-id | 20040517075834.H21709@megazone.bigpanda.com обсуждение исходный текст |
Ответ на | Re: a wierd query ("Stijn Vanroye" <s.vanroye@farcourier.com>) |
Список | pgsql-sql |
On Mon, 17 May 2004, Stijn Vanroye wrote: > Are you sure about that Edmund? > > I have the following query: > select distinct on (task_id, date) task_id, workhour_id, date from > ( > select task_id, workhour_id, begindate as date from workhour > UNION > select task_id, workhour_id, enddate as date from workhour > )as dist1 This gets you first rows distincted by task_id, workhour_id and date and then only rows distincted by task_id and date (and an unpredictable workhour_id). > if I use the query without the top level select, like this: > select task_id, workhour_id, begindate as date from workhour > UNION > select task_id, workhour_id, enddate as date from workhour This gets rows distincted by task_id, workhour_id and date.
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