Fixing the payout issue - sql

Question

I am re-posting my original question with edits, as that question was answered and best answer chosen.
Payments comes from our supplier which goes towards the accounts and the reps get paid based on which account got how much.
Customers Table (Usage is kwH)
+----+----------+------------+----------+----------+----------+-------+-------+
| ID | Customer | Account_no | Meter_no | Supplier | Active | Usage | Repid |
+----+----------+------------+----------+----------+----------+-------+-------+
| 1 | Joe | 123 | 111 | NSTAR | active | 20 | 100 |
| 2 | Joe | 123 | 222 | NSTAR | active | 30 | 100 |
| 3 | Joe | 123 | 150 | NSTAR | inactive | 60 | 100 |
| 4 | Sam | 456 | 352 | SEP | active | 50 | 100 |
| 5 | Jill | 789 | 222 | FES | active | 40 | 200 |
| 6 | Mike | 883 | 150 | ABB | inactive | 40 | 200 |
+----+----------+------------+----------+----------+----------+-------+-------+
Payment_Receive (table)
+------------+----------+-------------+-------------+
| Account_no | Supplier | Amount_paid | PaymentDate |
+------------+----------+-------------+-------------+
| 123 | NSTAR | 20 | 2011-11-01 |
| 456 | SEP | 40 | 2011-11-01 |
| 456 | SEP | -40 | 2011-11-01 |
| 456 | SEP | 40 | 2011-11-01 |
| 789 | FES | 50 | 2011-11-01 |
| 883 | ABB | 30 | 2011-11-01 |
+------------+----------+-------------+-------------+
The two tables are used for rep payout. Payment are recieved for each account, they are matched with our customers based on Account_No and Supplier. We do not have control over the payment_table because it comes from outside. This creates certain problems because we can not do one-to-one match between the two tables. Leaving that aside, I would like to have payout calculated for RepID = 100 with certain criteria. This is the output I would like to see for RepId = 100
+------------+----------+-------------+-------------+-------------+
| Account_no | Supplier | Amount_paid | Usage | PaymentDate |
+------------+----------+-------------+-------------+-------------+
| 123 | NSTAR | 20 | 60* | 2011-11-01 |
| 456 | SEP | 40 | 50 | 2011-11-01 |
| 456 | SEP | -40 | 40 | 2011-11-01 |
| 456 | SEP | 40 | 40 | 2011-11-01 |
+------------+----------+-------------+-------------+-------------+
Note here that
Account_no 123 exists thrice in customers table, it must show one time in rep payout
3 amounts were paid to account_no 456, all the three must show in the report
*60 = Notice that there are 2 active records (and one inactive). This could be the sum of the two active. But any other value is acceptable if that makes the query easy (for greater of the two or one, not the other)
Note that Usage column must appear in the output table, This is the column that creates problem for me. If I dont include this everything works fine.
The point with Usage column, if I have two records for same customer having same Account_No and Supplier but different usage, that makes the two records distinct when I include usage column. Therefore distinct does not work to remove this duplicate.
Reports are calculated on Monthly basis
Script for the question
create database testcase
go
use testcase
go
create table customers (
id int not null primary key identity,
customer_name varchar(25),
account_no int,
meter_no int,
supplier varchar(20),
active varchar(20),
usage int,
repid int
)
create table payments_received (
account_no int,
supplier varchar(20),
amount_paid float,
paymentdate smalldatetime
)
insert into customers values('Joe',123, 111,'NSTAR','active',20,100)
insert into customers values('Joe',123, 222,'NSTAR','active',30, 100)
insert into customers values('Joe',123, 150,'NSTAR','inactive',60,100)
insert into customers values('Sam',456, 352,'SEP','active',40,100)
insert into customers values('Jill',789, 222,'FES','active',40,200)
insert into customers values('Mike',883, 150,'ABB','inactive',40,200)
select * from customers
insert into payments_received values(123,'NSTAR',20,'2011-11-01')
insert into payments_received values(456,'SEP',40,'2011-11-01')
insert into payments_received values(456,'SEP',-40,'2011-11-01')
insert into payments_received values(456,'SEP',40,'2011-11-01')
insert into payments_received values(789,'FES',50,'2011-11-01')
insert into payments_received values(883,'ABB',30,'2011-11-01')
select * from payments_received

Answer 1

How about this:
CREATE VIEW v_customers_by_rep
AS
SELECT SUM(USAGE) AS USAGE ,
REPID ,
CAST(account_no AS VARCHAR) + '_' + Supplier AS UniqueId
FROM customers
GROUP BY CAST(account_no AS VARCHAR) + '_' + Supplier ,
REPID
GO
DECLARE
#repid INT
SET #repid = 100
SELECT pr.* ,
u.Usage
FROM payments_received pr INNER JOIN v_customers_by_rep u
ON CAST(pr.account_no AS VARCHAR) + '_' + pr.Supplier = u.UniqueId
WHERE u.repid = #repid
You could also eliminate inactive records in the view if desired.