Re: Sorting based on maximum value over several columns

Hi Greg,

Although it doesn't really seem to be a very well-structured database
design, I think there is a solution.

If the amount of fields is low, you can just stick a CASE in the MAX like:

SELECT ...,
MAX(
CASE WHEN value1 > value2 THEN
(CASE WHEN value1 > value3 THEN value1 ELSE value3 END)
ELSE
(CASE WHEN value2 > value3 THEN value2 ELSE value3 END)
END
) as sorter
FROM yourtable
GROUP BY ...
ORDER BY sorter

But if there are more than three values it will be a very long
CASE-statement and you're probably better off defining a FUNCTION. I'm
not sure whether it is possible to define a function with an unspecified
amount of inputvalues, but you can also use the table type as input type
and work with a table record in your function.
It might yield best performance, though, to create a C-function for this.

If there is already a "max of several fields"-function in PostgreSQL,
than you can use that of course.

Best regards,

Arjen

On 7-11-2004 1:31, Net Virtual Mailing Lists wrote:
> Hello,
>
> Lets say I have data like this:
>
>
> value1|value2|value3|value4|....|value(N)
> ------|------|------|------|----|--------
> 100 | 200 | 300 | 400 | |
> 10 | 20 | | 40 | |
> | 15 | | 16 | |
> 5 | | | | |
>
>
> Now I want to sort these based on the maximum value of the data in each
> row, so for sorting purposes I would have this:
>
> sort
> ----
> 400
> 40
> 16
> 5
>
>
> Any ideas?... I've tried several things but none of them have given me
> the result I am after....
>
>
> Thanks as always!
>
> - Greg
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo(at)postgresql(dot)org
>