Re: [Newbie] UPDATE based on other table content

Never mind, I found how finally:

UPDATE
product
SET
qty = qty+s_count
FROM (
SELECT
intermediate.product_id,
count(*) AS s_count
FROM
intermediate,
orders
WHERE
orders.intermediate_id=intermediate.id
GROUP BY
intermediate.product_id
) AS summary
WHERE
summary.product_id = product.id
;

Sorry for disturbance!
Daniel

Daniel Chiaramello a écrit :
> Hello.
>
> I have a very basic question, relative to the following "problem".
>
> I have the following tables:
>
> product
> id
> qty
>
> intermediate
> id
> product_id
>
> orders
> intermediate_id
>
> I want to update the "qty" field of the "product" table by
> incrementing it each time there is an order in the "orders" table,
> referencing a given product through the "intermediate" table.
>
> I tried the following request:
>
> UPDATE
> qty = qty+1
> FROM
> intermediate,
> orders
> WHERE
> orders.intermediate_id=intermediate.id AND
> intermediate.product_id=product.id
> ;
>
> But of course it does what was predictable - ie the qty "field" is
> incremented only once, even if more than one entry is referencing a
> given product. But it's not what I was hoping...
>
> What would be the "good" solution to do that UPDATE?
>
> Thanks for your attention!
> Daniel Chiaramello
>