Re: Primary key and references

On Tuesday 18 Mar 2003 8:07 pm, Nigel J. Andrews wrote:
> On Tue, 18 Mar 2003, Shridhar
Daithankar<shridhar_daithankar(at)persistent(dot)co(dot)in> wrote:
> > I consider this as a bug but given my understanding of sql, I won't count
> > on it. Any comments?
>
> If a is to be referenced in a foreign key it needs to be unique or how
> could it it be known which of the rows with a given value are being refered
> to. It follows that if a can be referenced in a foreign key then a uniquely
> identifies a row in the referenced table and therefore a primary key of
> (a,b) necessarily is unique based solely on a, i.e. the (a,b) combination
> seems unlikely to be the primary key for the table.

Hmm.. So I need to create unique constraint on original column. OK. Got it
now..

Shridhar