An aggregate may not appear in the WHERE clause (MSSM studio) - sql

Question

I am trying to create a trigger for insert on Advertisement table. When trying to write this cursor
declare Users cursor for
Select "User".IDUser, Sum(Price)
from "User"
inner join Purchase as pu on "User".IDUser = pu.IDUser
inner join PurchaseProduct as pp on pu.IDPurchase = pp.IDPurchase
inner join Product as pr on pp.IDProduct = pr.IDProduct
inner join inserted on pr.IDProduct = inserted.IDProduct
where pr.ProductType = (select ProductType
from Product
inner join Advertisement on Product.IDProduct = Advertisement.IDProduct
inner join inserted on Advertisement.IDProduct = inserted.IDProduct
where Advertisement.IDAdvertisement = inserted.IDAdvertisement)
and Sum(Price) > 50;
I get this error
Msg 147, Level 15, State 1, Procedure AutomaticUserAdvertisementScoreCalculating, Line 15 [Batch Start Line 113]
An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.
What might be the error here? Below you can see my DB structure
Thanks in advance

Answer 1

You could use HAVING to filter rows after aggregation:
declare Users cursor for
Select "User".IDUser, Sum(Price) from "User"
join Purchase as pu on "User".IDUser = pu.IDUser
join PurchaseProduct as pp on pu.IDPurchase = pp.IDPurchase
join Product as pr on pp.IDProduct = pr.IDProduct
join inserted on pr.IDProduct = inserted.IDProduct
where pr.ProductType = (select ProductType from Product
join Advertisement on Product.IDProduct = Advertisement.IDProduct
join inserted on Advertisement.IDProduct = inserted.IDProduct
where Advertisement.IDAdvertisement = inserted.IDAdvertisement)
GROUP BY "User".IDUser
HAVING Sum(Price) > 50;