Re: SUM the result of a subquery.

> SELECT SUM (
> (SELECT i.id_item, i.price, SUM (o.quantity), ROUND (SUM
> (o.quantity) * i.price, 2) AS cost
> FROM orders o
> JOIN items i ON i.id_item = o.id_item
> WHERE o.date_order BETWEEN '2010-01-01' AND '2010-01-31'
> GROUP BY i.id_item, i.price)
> );
>
> No luck. Obviously SUM expects an expression, not a set of rows. Is
> there a way to perform a sum of the resulting rows?
>
I don't have a PostgreSQL server to try this right now. But you are
looking for something like
SELECT SUM (cost) from (
(SELECT i.id_item, i.price, SUM (o.quantity), ROUND (SUM (o.quantity) *
i.price, 2) AS cost
FROM orders o
JOIN items i ON i.id_item = o.id_item
WHERE o.date_order BETWEEN '2010-01-01' AND '2010-01-31'
GROUP BY i.id_item, i.price)
) as x

Regards,
Jayadevan

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