I have a clients table which consists of, among other things, a column
named source.

I have a second table, sources, with two columns - client_id and source.

The are fewer rows in sources than in clients. I am trying to update
clients.source with sources.source without affecting the clients that
do not have a corresponding row in sources.

My first try was update clients set clients.source = sources.source
where clients.client_id = sources.client_id

But I ended up with nulls in the clients.source column for rows in
which there was no row in sources.

I am guessing that I need to involve a join somehow, but I am having a
very hard time not thinking procedurally, and just don't "get" it.

I've been looking at Join examples, but anything non-trivial just
baffles me. Would someone be so kind as to explain how to do what I'm
trying to do?

Thanks.

-Steve

In article <466f16f2$0$90276$14726298 (AT) news (DOT) sunsite.dk>, Nis Jørgensen
<nis (AT) superlativ (DOT) dk> wrote:

Yes it does. Thank you very much.
So let me try to understand how it works (using the second version).
First it finds the set of clients who have a corresponding row in
sources (the 'outside' part of the statement), then it updates the
column using the 'inner' select?

I am finding it difficult to think in terms of sets and 'simultaneous'
actions. I keep wanting to solve these things procedurally.

Thanks again.

It takes about a year to have the revelation My next book will
deal with thinking in sets. Hey, remember how weird recurson was?