List Concatination

Folks,

I have an interesting problem. For purpose of presentation to users,
I'd like to concatinate a list of VARCHAR values from a subtable. To
simplify my actual situation:

CREATE TABLE clients (
client_id SERIAL PRIMARY KEY,
client_name VARCHAR(50) );

CREATE TABLE client_contacts (
contact_id SERIAL PRIMARY KEY,
client_id REFERENCES clients(client_id),
first_name VARCHAR(25),
last_name VARCHAR(25) );

CLients:
1 McMurphy Assoc.
2 Ross Construction

Contacts
1 1 Jim Henson
2 1 Pat O'Gannet
3 2 Sara Vaugn
3 2 Bill Murray

etc.

What I'd like to be able to do is present a list of clients and their
comma-seperated contacts in paragraph form, hence:

Client Contacts
McMurphy Assoc. Jim Henson, Pat O'Gannet, Kelley Moore

Ross Construction Sara Vaugn, Bill Murray, Peter Frump,
Siskel Ebert

I can figure out how to do this procedurally (using PL/pgSQL and a
cursor) but not how to do it declaratively (using only SQL). The reason
it's important to do it declaritively is that there are actually two
sub-tables with thousands of entries and the procedural approach is
rather slow.

Suggestions?

-Josh Berkus

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