Re: DEFERRABLE NOT NULL constraint

Gavan Schneider wrote:
> But I feel I have missed something here.
>
> Referring to:
> <http://www.postgresql.org/docs/current/static/sql-createtable.html>

> CHECK constraints, NOT NULL constraints and FOREIGN KEY
> constraints all look very deferrable in this definition. If
> that's the case, why are we having this discussion if the
> requested functionality/compliance is already present? (As I
> have said already) I really must have missed something so am
> standing by for the 'gotcha'... please supply :)

Further down on the page you quote, it says:

DEFERRABLE
NOT DEFERRABLE

This controls whether the constraint can be deferred.
A constraint that is not deferrable will be checked
immediately after every command. Checking of constraints
that are deferrable can be postponed until the end of
the transaction (using the SET CONSTRAINTS command).
NOT DEFERRABLE is the default. Currently, only UNIQUE,
PRIMARY KEY, EXCLUDE, and REFERENCES (foreign key)
constraints accept this clause.
NOT NULL and CHECK constraints are not deferrable.

Yours,
Laurenz Albe