That is because your query is generating a cartesian product. Try:
SELECT ( SELECT SUM(totalprice) FROM invoices WHERE custnumber = '1' ) - ( SELECT SUM(paymentamount) FROM payments WHERE custnumber = '1' ) Roy Souther wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > I have an invoice database that has two tables one for invoices and one for > payments. I want to get the account balance for a client by subtracting the > sum of all payments from the sum off all invoices for that client. > > Here is the SQL that I thought should work. > SELECT SUM(t0.totalprice)-SUM(t1.paymentamount) FROM invoices t0, payments t1 > WHERE t0.custnumber='1' AND t1.custnumber='1' > > It works fine if there is only one invoice and one payment but as soon as > there is more then one of either it screws up. For each match found in > payments the invoice sum is added to the total. So if client 1 purchased a > $100 item then maid a $10 payment the SQL would return the balance of $90 > just fine. When the client makes a second payment of $15 the balance is $75 > but this SQL returns ($100+$100)-($10+$15) = $175. A third payment of $1 > would return ($100+$100+$100)-($10+$15+$1) = $274. > > Could some one explain this to me and recommend an SQL command that would work > please? I could do this using a temp table but that would be very messy as I > would really like it to be a single SQL command. > - -- > Roy Souther <[EMAIL PROTECTED]> > http://www.SiliconTao.com > > Linux: May the source be with you. > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.0.6 (GNU/Linux) > Comment: For info see http://www.gnupg.org > > iEYEARECAAYFAj0oo9MACgkQCbnxcmEBt43qFQCgtjCs7khKGH+2LYd78O9mA3h4 > vDQAn0GkKkuYl1Kybgm/ITO4LbO1WWLX > =1G4R > -----END PGP SIGNATURE----- > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED] ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
