Re: SQL Question

Heh, scratch that, the EXISTS query DOES work. Is this the most efficient
way to perform this kind of query? Thanks!

On Tue, Apr 1, 2014 at 1:21 PM, Robert DiFalco <robert(dot)difalco(at)gmail(dot)com>wrote:

> I have two queries I would like to combine into one.
>
> I have a table that represents a user's contacts. It has fields like "id,
> owner_id, user_id". Owner ID cannot be null but user_id can be null. They
> are numeric field, the ID is just generated.
>
> I want a query to retrieve all of a user's contacts but add in a field to
> know if there is a mutual relationship between the contact owner.
>
> I get all of a user's contacts like this:
>
> SELECT c.* FROM contacts c WHERE c.owner_id = :id;
>
> I can then get all contacts that have the owner as a user like this:
>
> SELECT c.* FROM contacts c WHERE EXISTS(
> SELECT 1 FROM contacts c2 WHERE c2.user_id = c.owner_id AND
> c2.owner_id = c.user_id)
> AND c.owner_id = 1;
>
> But what I'd like is to have the EXISTS clause of the second query to show
> up as a BOOLEAN field in the result set. I don't want it to scope the
> results, just tell me for each contact of the owner, do they also have her
> as a contact?
>
> I tried this but it didn't work:
>
> SELECT c.*, EXISTS(SELECT 1 FROM contacts c2 WHERE c2.owner_id =
> c1.user_id AND c2.user_id = c1.owner_id)
> WHERE c.owner_id = :owner;
>
> Thanks!
>
>