Re: foreign key restrictions

rafal@zorro.isa-geek.com writes:
>> The reason why is that the SQL spec says so:
>>
>> a) If the <referenced table and columns> specifies a
>> <reference
>> column list>, then the set of <column name>s contained
>> in that <reference column list> shall be equal to the
>> set of <column name>s contained in the <unique column
>> list> of a unique constraint of the referenced table.

> I must admit, the standard is not very easy reading for me; what exactly
> does the standarad mean by "<unique column list>":
> 1. is that a requirement for mathematical properties of that list, or

The point is it says "shall be equal to", not "shall be a superset of".

            regards, tom lane