Tom Ha wrote:
> Hi there,
>
> I have the following tables...
>
> User :has_many Purchases
> Item :has_many Purchases
>
>
> ...where Item has a column "amount" (can be + or -) and I need to find
> all Users that have a positive SUM of "amounts" (over all Purchases each
> one has made).
>
> How does this query look like? (I'm not sure how to handle "SUM"
> correctly, in this case.)
@user # assume this exists
total = Purchase.sum(:amount, :conditions => { 'user_id' => @user })
=> SELECT sum("purchases".amount) AS sum_amount FROM "purchases" WHERE
("purchases"."user_id" = 1)
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