MYSQL, Creating a view and pulling information from two tables - mysql

Question

Okay so I have two tables:
hscust and hssales_rep
I need to create a view that shows me the reps fname and lname (as well as the customers) and show how much the customer is over on there credit balance.
This is the code I have:
CREATE VIEW OverLimit AS
SELECT
CONCAT(hssales_rep.last,hssales_rep.first) AS Rep,
CONCAT(hscust.last,hscust.first) AS Cust,
SUM(credit_limit - balance)
FROM hscust
INNER JOIN hssales_rep ON hscust.sales_rep = hssales_rep.repid
And it returns an empty result.
Any help is greatly appreciated!
salesrep table
cust table

Answer 1

A CREATE VIEW statement doesn't return a resultset.
A SELECT statement can return an empty resultset. But we'd expect the SELECT statement in your view definition to return either a single row, or throw an error.
I suggest you break this down a bit.
1) What problem is being solved by the CREATE VIEW statement. Why do you need a view?
2) Before you write a CREATE VIEW statement, first develop and test a SELECT statement that returns the required resultset. Do that before you put that into a view definition.
I also strongly recommend that you qualify all column references in the SELECT statement either with the table name or (preferably) a short table alias.
If you want to return a row for each Cust with an aggregate function (e.g. SUM) in your SELECT list, then add an appropriate GROUP BY clause to your SELECT statement.
It's not clear why we would want to use a SUM aggregate function.
The difference between "credit_limit" and "balance" would be the available (remaining) credit. A negative value would indicate the balance was "over" the credit limit.
SELECT CONCAT(r.last,r.first) AS Rep
, CONCAT(c.last,c.first) AS Cust
, c.credit_limit - c.balance AS available_credit
FROM hscust c
JOIN hssales_rep r
ON c.sales_rep=r.repid
ORDER
BY CONCAT(r.last,r.first)
, CONCAT(c.last,c.first)
, c.custid
If we only want to return rows for customers that are "over" their credit limit, we can add a WHERE clause.
SELECT CONCAT(r.last,r.first) AS Rep
, CONCAT(c.last,c.first) AS Cust
, c.credit_limit - c.balance AS available_credit
FROM hscust c
JOIN hssales_rep r
ON c.sales_rep=r.repid
WHERE c.credit_limit - c.balance < 0
ORDER
BY CONCAT(r.last,r.first)
, CONCAT(c.last,c.first)
, c.custid
Again, get a SELECT statement working (returning the required resultset) before you wrap it in a CREATE VIEW.