Aggregation and joining 2 tables or Sub Queries

Question

I have the following tables.

Order_table

Order_ID	Item_ID	Qty_shipped
1111	11	4
1111	22	6
1111	33	6
1111	44	6

Shipping_det

Order_ID	Ship_num	Ship_cost
1111	1	16.84
1111	2	16.60
1111	3	16.60

I want my output to be as follows,

Order ID	Qty_shipped	Ship_cost
1111	22	50.04

I wrote the following query,

select sum(O.qty_shipped) as Qty_shipped, sum(S.Ship_cost) as Total_cost
from Order_table O
join shipping_det S on O.Order_ID = S.Order_ID

and I got my output as

Qty_shipped	Total_cost
66	200.16

As per my understanding, because I joined the two tables, Qty_shipped got multipled 3 times and Total_cost got multiplied 4 times.

Any help would be appreciated.

Thanks in advance.

Answer 1

You need to aggregate before joining. Or, to union the table together and then aggregate:

select order_id, sum(qty_shipped), sum(ship_cost)
from ((select order_id, qty_shipped, 0 as ship_cost
       from order_table
      ) union all
      (select order_id, 0, ship_cost
       from shipping_det
      )
     ) os
group by order_id;