Re: How to union tables and have a field with UNIQUE constraint?

On Fri, 28 Dec 2001, Katona Gabor wrote:

>
>   I have the followinig SQL code (of course the tables contain more useful
> data). When I load it into PostgreSQL via \i foo.txt it produces the
> folloving error massage:
> UNIQUE constraint matching given keys for referenced table "t" not found
>   The task I want to do with this code: Making a table t from t1 and t2 using
> the id and the foo column. Table t shoud have one id and one foo column,
> holding all the rows from t1 and t2, this is why I use UNION. As you can see,
> the id column of t1 and t2 is PRIMARY KEY, therefore UNIQUE and the prepared
> sequences provide that no rows can share the same id even after UNION.
>
>   How can I correct the code to work? Is there any working way of doing such
> things?

I assume you want to reference id, so you'd need to do something like:

CREATE UNIQUE INDEX t_id_key ON t(id);
and in the uniont definition, something like:
tid INTEGER REFERENCES t(id),

This is a hacky sort of way to do it (we allow you to make the internal
form that a unique constraint has via create index even on views which
I don't believe would ever be used :( ) and may not continue working
forever.