SQL query summation

Question

I have two tables

Unit

Unit_id
Unit_name
Unit_cost

Components

Component_id
Component_         


        

Answer 1

assuming that unit cost should be multiplied by number of related components:

select top 1 name from(
select u.unit_name AS name, count(c.component_id) * u.unit_cost AS cost
from unit u join components c on u.unit_id = c.unit_id)
order by cost desc

In the inner query name and unit cost is calculated, at the outer query mname for unit that have max cost is selected. If cost should be calculated in some other way just change count(c.component_id) * u.unit_cost formula in the query

Answer 2

I think you want something like this:

select top (1) u.unit_name
from unit u join
     component c
     on c.unit_id = u.unit_id
group by u.unit_id, u.unit_name
order by sum(c.cost) desc;