Re: distinct
От | John McKown |
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Тема | Re: distinct |
Дата | |
Msg-id | Pine.LNX.4.21.0010091903240.28048-100000@linux2.johnmckown.net обсуждение исходный текст |
Ответ на | distinct ("Otwell, Andrew (ISSAtlanta)" <AOtwell@iss.net>) |
Список | pgsql-general |
On Tue, 3 Oct 2000, Otwell, Andrew (ISSAtlanta) wrote: > I have attempted to run > select distinct col1 from tablename; > and it runs fine. > > When I run it in a real world environment: > select distinct col1, col2, col3, col4 from tablename order by col1 desc, > col2; > It returns all the values from col1 which appears to be the same thing as > not using distinct at all. > > Am I missing something? I'd like only distinct values on col1 and then I'll > sort, include, or exclude the other columns. The DISTINCT keyword means that the row returned (all values considered together) is DISTINCT. Not just that the first variable is DISTINCT. So a row having values of 'a','b' and another row with 'a','c' are distinctly different in that the second variable is not the same. I don't know of a way to say that you want "col1" to be distinct. In the above case, which row should be returned? I.e. if there are two different values for col2, which single one is returned? random? lowest value? I hope this makes sense, but I fear that I didn't do a good job of explaining. John
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