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

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.