Обсуждение: Random sort with distinct

I have the following query

 

Select Distinct VehicleMake, VehicleModel

From VehicleYearMakeModelTrim

Order by random()

Limit 10;

 

I don’t want to bring back the random number I just want the sort order to be random. How can I sort randomly?  This query breaks because random() is not in the select.

 

Thanks

 

Pam

-- 
Lee Hachadoorian
PhD Student, Geography
Program in Earth & Environmental Sciences
CUNY Graduate Center

"Ozer, Pam" <pozer@automotive.com> writes:
> Select Distinct VehicleMake, VehicleModel
> From VehicleYearMakeModelTrim
> Order by random()
> Limit 10;

> I don't want to bring back the random number I just want the sort order
> to be random. How can I sort randomly?  This query breaks because
> random() is not in the select.

Well, yeah: the implication of the ORDER BY is that a new random value
is to be computed for each row of VehicleYearMakeModelTrim.  After you
combine rows with DISTINCT it's not clear which of those values should
be used to sort a grouped row.

You need to put the DISTINCT and the ORDER BY in separate query levels,
like this:

select * from (Select Distinct VehicleMake, VehicleModel  From VehicleYearMakeModelTrim) ss
Order by random()
Limit 10;
        regards, tom lane