> On Sep 29, 2019, at 1:52 PM, John W Higgins <wish...@gmail.com> wrote:
>
> On Sun, Sep 29, 2019 at 12:40 PM stan <st...@panix.com
> <mailto:st...@panix.com>> wrote:
> I have a table that consists of 3 columns.
>
> vendor_key
> mfg_key
> preferred (boolean)
>
> The idea is that a given vendor is the vendor we want to use for each
> manufacturer for a given project.
>
> I need to constrain such that only on row of mfg, vendor and project can
> be set to TRUE.
>
>
> Partial unique index
>
> Example 3 on this page
> https://www.postgresql.org/docs/current/indexes-partial.html
> <https://www.postgresql.org/docs/current/indexes-partial.html> is exactly
> what you are looking for.
>
> John W Higgins
>
Yes but I have to wonder about one-and-only-one preferred vendor: if there are
many known, acceptable vendors, wouldn’t a ranking be more useful? On a
crucial commodity it is common practice to continuously use more than one
vendor (i.e. multiple preferred vendors).
