Moshe Jacobson <moshe(at)neadwerx(dot)com> writes:
> Take the following table:
>
> CREATE TABLE exclusion_example AS
> (
> pk_col integer primary key,
> fk_col integer not null references other_table,
> bool_col boolean not null
> );
>
> I want to ensure that for any given value of fk_col that there is a maximum
> of one row with bool_col = true.
This should be what you want:
ALTER TABLE exclusion_example
ADD CONSTRAINT ex
EXCLUDE (fk_col WITH =) WHERE (bool_col);