help on a query

Hi all,

This is one of those things I know I should know, but it's not coming to
me. It's probably really simple.

I have two related tables, registrations and receipts, related by the
field registration_id.

So registrations looks kinda like:

registration_id bigint (primary key)
foo varchar(10)
bar varchar(20)

and receipts looks like:

receipt_id bigint (primary key)
registration_id bigint (foreign key)
amount float
baz varchar(10)

If someone has paid, there is a row in the receipts table for that
registration ID#.

I need to find a list of the registration IDs that *don't* have an entry
in the receipts table.

Thanks in advance!!!
--
.Michelle

--------------------------
Michelle Murrain
mmurrain at dbdes dot com
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"I see all the different religious traditions as paths for the
development of inner peace, which is the true foundation of world peace.
These ancient traditions come to us as a gift from our common past. Will
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generations as a legacy of our shared desire for peace?" - His Holiness
the Dalai Lama