Hengky Lie wrote > 1. I want to select all productID from Table A where supplierID='XXX'. > > 2. Based on list from Step.1 : sum the initialstock from Table B > > 3. Based on list from Step 1 : Sum (in-out) from Table C where date > <'BEGINNING DATE' > > 4. Based on list from Step 1 : Sum (in) and sum(out) from Table C where > date between 'BEGINNING DATE' and 'ENDING DATE' You have three questions so you'll likely need three queries. You can combine them for final output if desired. You can use multiple direct sub-queries or use CTEs/WITH. Note that table B seems pointless. All stock should initially be zero and the first IN record in Table C establishes the initial balance. That said I've used a similar schema before so having a starting balance column may have merit. But why not put in on Table A instead? David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/Sum-2-tables-based-on-key-from-other-table-tp5778813p5778820.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
