SQL How to Update SUM of column over group in same table

Question

I have a (SQL Server) table similar to the following:

SalesSummary

Year | Team | Person | Person Sales | Team Sales/Yr

2013     

Answer 1

Try this.

UPDATE  SalesSummary SET TeamSales = (Select Sum(PersonSales) 
        From    SalesSummary S 
        Where S.Year=SalesSummary.Year AND S.Team=SalesSummary.Team)

Answer 2

I have a table variable instead a regular table, therefore I needed to adapt @Shell's answer a bit - so my solution for the question's problem when the table is a variable:

Update SU
Set TeamSales = (Select Sum(SI.PersonSales) 
                 From   @SalesSummary SI 
                 Where  SI.Year=SU.Year AND SI.Team=SU.Team)
From @SalesSummary SU

Answer 3

Assuming you are using SQL Server, I think you want something like this:

WITH toupdate AS
     (SELECT team, year, 
             Sum(personsales) OVER (partition BY team, year) AS newTeamSales 
      FROM salessummary
     ) 
UPDATE toupdate 
   SET teamsales = newteamsales; 

Your original query has several issues and suspicious constructs. First, an aggregation subquery is not updatable. Second, you are doing an aggregation and using a window function with, although allowed, is unusual. Third, you are aggregating by PersonSales and taking the sum(). Once again, allowed, but unusual.