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link管理  ›  SELECT DISTINCT and ORDER BY - PostgreSQL Inc.: PostgreSQL - Tek-Tips
distinct select
https://www.tek-tips.com/viewthread.cfm?qid=1261181
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    SELECT DISTINCT and ORDER BY

    thread699-1261181
    Forum Search Links
    Hi everyone,

    i have amongst others the columns pid(varchar) and insertDate(timestamp) and would like to obtain all distinct pid values ordered by insertDate. The problem, though, is that with the following query

    CODE

    select distinct pid, insertDate from mytable order by insertDate
    returns all distinct combinations for pid and insertDate. But i want ONLY the distinct pids ordered by the timestamp.

    Any advice is really appreciated.

    RE: SELECT DISTINCT and ORDER BY

    I tried that but it seems not to work with order by. That's the error i get when i include the order by:
    SELECT DISTINCT ON expressions must match initial ORDER BY expressions

    RE: SELECT DISTINCT and ORDER BY

    Hi

    As far as I remember, this was my first question on Tek-Tips in thread699-434666 . smile

    But since then, I did not find out the solution. The best workaround is using sub-select :

    CODE

    select * from (
    select distinct on (pid) pid, insertDate from mytable
    ) foo order by insertDate

    Feherke.
    http://rootshell.be/~feherke/

    RE: SELECT DISTINCT and ORDER BY

    Thanks that worked!!

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