As usual, works like a charm.

The conditional index works as expected in PostgreSQL too, so it's all
good.

What methods should I be looking at so I can try and figure some of
this stuff out myself.

I also want a constraint on a table that for a boolean value, only one
can be set to true at one time per each individual foreign key and I
have a bunch of triggers I want to write to make totals tables on
inserts and updates. In general I like to not have to use raw SQL, but
since I will be using PostgreSQL and only PostgreSQL for this project,
I don't mind having to do a little bit if I need to. (And I am so glad
I don't have to deal with MSSQL this time around.)

On Feb 6, 8:43 pm, Jeremy Evans <[email protected]> wrote:
> On Feb 6, 1:35 pm, cult hero <[email protected]> wrote:
>
> > I'm trying to get more and more into the habit of moving a lot of my
> > constraints to the database instead of having them in the application.
> > However, for all but the most simple constraints (unique, for
> > instance) I'm trying to figure out the code for the implementation in
> > my migrations.
>
> > For instance, I want to create some compound unique fields (as in the
> > combination of the two fields is unique just like a compound primary
> > key).
>
> A unique index will do that:
>
>   index [:col1, :col2], :unique => true
>
> > And, is it possible to make the constraints conditional? Such as a
> > compound field but the uniqueness is ONLY checked if a third boolean
> > field is set to true. As a result if the field is false the uniqueness
> > of the two doesn't matter.
>
> Some databases support partial unique indexes:
>
>   index [:col1, :col2], :unique => true, :where => :col3
>
> Jeremy

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