Обсуждение: Multiple columns w/single aggregate

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Multiple columns w/single aggregate

От
"Robert M. Craver II"
Дата:
I cannot successfully execute the sql statement:

SELECT percentage, MAX(start_date) FROM sometable
WHERE id = 1

I get the error message:

   ERROR: Attribute sometable.percentage must be GROUPed
   or used in an aggregate function

I know that I have seen examples of selecting multiple columns with a
single colunn aggregate function.  In fact, the new 'PostgreSQL:
Introductions and Concepts' book by Bruce Momjian has two on page 53.
Does anyone know why this doesn't work?

Thanks in advance.

Re: Multiple columns w/single aggregate

От
Bruce Momjian
Дата:
> I cannot successfully execute the sql statement:
>
> SELECT percentage, MAX(start_date) FROM sometable
> WHERE id = 1

Sure, you need GROUP BY.  How does it know which columns to use for the
MAX.

>
> I get the error message:
>
>    ERROR: Attribute sometable.percentage must be GROUPed
>    or used in an aggregate function
>
> I know that I have seen examples of selecting multiple columns with a
> single colunn aggregate function.  In fact, the new 'PostgreSQL:
> Introductions and Concepts' book by Bruce Momjian has two on page 53.
> Does anyone know why this doesn't work?
>
> Thanks in advance.
>
>


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