Re: Implementing DB2's "distinct" types

>> create type sno as varchar(50)
>> with comparisons;
>>
>> create type pno as varchar(50)
>> with comparisons;
>>
>> The following query will be rejected because sno and pno are not comparable (even though both are varchar columns):
>>
>> select *
>> from p
>> join s on s.sno = p.pno;
>>
>> I wonder if a similar behaviour can be achieved with Postgres' types as well.
>>
>> As a type definition in Postgres can also include comparison functions, I have the feeling that
>>this should be possible, but I don't have an idea on how to start to be honest.
>>
>
> Please mark this to pgsql-hackers, where you might get much better constructive feedback.
>
> It does sound nice.

I'm more interested if this can be dealt with on SQL level, rather than hacking Postgres itself
(and it's not really a "request" for a new feature - I'm just curious)

Thomas

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