Re: Strange limit and offset behaviour.... - Mailing list pgsql-general

From Adam Rich
Subject Re: Strange limit and offset behaviour....
Date
Msg-id 0cbf01c9896e$005ecaf0$011c60d0$@r@sbcglobal.net
Whole thread Raw
In response to Strange limit and offset behaviour....  (Bjørn T Johansen <btj@havleik.no>)
Responses Re: Strange limit and offset behaviour....
List pgsql-general
>
> I have the following sql:
>
> SELECT * from table order by dato asc limit 20 offset 0
>
>
> This gives me different rows than the 20 first rows when running the
> following sql:
>
> SELECT * from table order by dato asc
>
>
> Shouldn't the 20 first rows in the second sql statment be the same 20
> rows that is returned in the first statement
> or am I missing something?
>

Not necessarily.  In your example query, if "dato" was not a unique
column, and there were some duplicates, the "top 20" values is not
a defined set.  Adding the offset clause might cause a different
query plan, resulting in a different ordering of the duplicate values.






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