SQL Server - Select Multiple Rows Data From One Table And Update Multiple Rows Data On Another Table With First Selected Data

SQL Server 2008 R2

I am going to explain it as simple as possible. Now I have a table_1 which has price and itemId. I also have another table table_2 which has totalprice,itemId.
What I want to do is to sum all price from table_1 grouped by itemId and update that sum of price in table_2 with itemId key as the common column.

The price per itemId summed from table_1 should update the totalprice column in table_2

You can do like this:


You can do like this:

update T2
set totalprice = T1.totalprice
from Table_2 as T2
  inner join (select sum(price) as totalprice,
                     itemid
              from Table_1
              group by itemid) as T1
    on T2.itemid = T1.itemid

If you don't already have all itemid's in table_2 you can use a merge to update the existing rows and add a new row if it is missing.

merge Table_2 as T2
using (select sum(price) as totalprice,
              itemid
       from Table_1
       group by itemid) as T1
on T1.itemid = T2.itemid
when matched then 
  update set totalprice = T1.totalprice
when not matched then 
  insert (totalprice, itemid) 
  values(T1.totalprice, T1.itemid);

I love MSSQL