Re: Question About UNION

Raymond O'Donnell wrote:
> On 09/10/2008 17:36, Bill Thoen wrote:
>
>> I'm trying to combine two tables, but I only want unique records based
>> on the first two columns. Can UNION be used to join three-column tables
>> but only include records based on the uniqueness of the first two
>> columns? If not, how would I do this with PostgreSQL 8.1?
>>
>
> How do you decide which records you want? - e.g. given the following rows...
>
>   (a, b, c)
>   (a, b, d)
>
> ...how do you decide whether you the one with c or the one with d?
>
>
The physical order that they appear will take care of that.