sum query - Mailing list pgsql-sql

From Keith Worthington
Subject sum query
Date
Msg-id 20041203213340.M8095@narrowpathinc.com
Whole thread Raw
Responses Re: [despammed] sum query
List pgsql-sql
Hi All,

I am trying to join three tables and sum the quantities.

The first table contains all of the possible items.  The second table contains
orders and the third table contains the items on each order.

For all items found in tbl_item I need the total quantity on open orders.  If
an item is not on any open order the quantity should be zero.

Can someone please explain the best way to do this?

tbl_item
id    | ...
------+...
AB12  | ...
CD34  | ...
EF34  | ...
GH12  | ...
JK56  | ...

tbl_order
order | closed |...
------+--------+...   1 | false  |...   2 | true   |...   3 | true   |...   4 | false  |...   5 | false  |...

tbl_item
order | id    | quantity
------+-------+---------   1 | AB12  | 10   1 | CD34  |  5   2 | CD34  |  3   3 | EF34  |  2   3 | GH12  | 20   4 |
GH12 |  4   5 | AB12  |  5
 

id    | quantity
------+---------
AB12  | 15
CD34  |  5
EF34  |  0
GH12  |  4
JK56  |  0

Kind Regards,
Keith 


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