Strange Query Question

Hello,

I found a query in some code that I am evaluating:

$query = qq|SELECT ap.id, ap.invnumber, vendor.name,
acc_trans.transdate, ap.invoice, acc_trans.amount
FROM ap, acc_trans
WHERE $where
AND acc_trans.accno = $form->{accno}
AND acc_trans.trans_id = ap.id
AND ap.vendor = vendor.id|;

The code executes properly, but I do not see how this query can work
without a FROM reference to the vendor table. How does this happen?

I do not understand how you can have a reference to 'vendor.id' here
with reference to the vendor table (which does exist in the database).

Incidently, '$where' is set to 'true' in previous code prior to building
the query.

Thanks,
Murrah Boswell