SQL brings more than one row of the same data - sql-server

Question

I tried researching before asking, but couldn't find anything or maybe I used the wrong keywords. I might get a -1 for that, but anyway.
In the exercise I'm doing I need to select the following expression
salary + comission value + trip expenses - discounts.
This is my select:
select a.id_vendor, a.name_vendor, a.id_region, a.salary + b.value + c.value - d.value
from vendors a
inner join comission b
on a.id_vendor = b.id_vendor
inner join trip_expenses c
on a.id_vendor = c.id_vendor
inner join discounts d
on a.id_vendor = d.id_vendor
group by a.id_vendor, a.name_vendor, a.id_region, a.salary, b.value, c.value, d.value;
I've tried adding sum to some of the number records, but didn't work.
The thing is, that when I execute this select it brings more than one record for the same Vendor ID, and I would like that they be summed into just one column.
This is the result:
id_vendor name_vendor id_region
----------- ------------------------------ ----------- ---------------------------------------
1 Marco 1 1955.00
1 Marco 1 2180.00
2 Walesca 2 3190.00
3 Carol 3 4970.00
4 Evelyn 4 1860.00
5 Wallace 5 10130.00
As you can see, Marco comes twice because he has more than one record on the discounts table.
How do correct that? What's wrong with my select?
Thanks in advance!

Answer 1

Without seeing the structure of your discounts table, it is hard to provide a definitive answer.
That said, and assuming that you have date ranges or some other indicator of when the discount should be applied, add that to your query in a where clause.
select a.id_vendor, a.name_vendor, a.id_region, a.salary + b.value + c.value - d.value
from vendors a
inner join comission b
on a.id_vendor = b.id_vendor
inner join trip_expenses c
on a.id_vendor = c.id_vendor
inner join discounts d
on a.id_vendor = d.id_vendor
-- Add a where clause looking at Start/End Dates
where d.StartDate < GetDate() and getdate() < d.EndDate
group by a.id_vendor, a.name_vendor, a.id_region, a.salary, b.value, c.value, d.value;
Hopefully this helps. If not, you may have to post your schema for your tables so we have a better idea of what you are working with.