multi-inner join statement - sql

Question

I'm currently trying to draw multiple tables through several inner-join statements. However, I am continually hit with the following error:
ORA-00904: "PART"."ITEM_CLASS": invalid identifier
I've visited several other pages here but that problem did not coincide with mine.
Here is the SQL query:
SELECT Slsrep_Number, AVG(Commission_Rate) AS AVG_Rate, MAX(Total_Commission) as MAX_Comission
FROM Sales_Rep
WHERE Sales_Rep.Slsrep_Number = Customer.Slrsrep_Number
AND Customer.C_Number = Orders.C_Number
AND Orders.Order_Number = Order_Line.Order_Number
AND Order_Line.Part_Number = Part.Part_Number
AND Part.Item_Class = 'SG';
Here are the tables being used (screenshots):
The pictures are listed in the order that I am referencing them in the SQL query.

Answer 1

You need to reference the tables in the FROM clause. You can't just reference them.
You should also use table aliases and proper, explicit, standard JOIN syntax.
So:
SELECT sr.Slsrep_Number,
AVG(?.Commission_Rate) AS AVG_Rate,
MAX(?Total_Commission) as MAX_Comission
FROM Sales_Rep sr JOIN
Customer c
ON sr.Slsrep_Number = c.Slrsrep_Number JOIN
Orders o
ON c.C_Number = o.C_Number JOIN
Order_Line ol
ON o.Order_Number = ol.Order_Number
Part p
ON ol.Part_Number = p.Part_Number
WHERE p.Item_Class = 'SG';
The ? is for the alias for the column with the commission.
The query now "looks" right. However, I don't think it is particularly useful. If that is the case, ask another question and provide sample data, desired results, and an explanation of what you want to accomplish.

Answer 2

Customer,Orders,Order_Line and Part Tables are missing in the from clause.Try This.
SELECT Slsrep_Number,
AVG(Commission_Rate) AS AVG_Rate,
MAX(Total_Commission) as MAX_Comission
FROM Sales_Rep,Customer,Orders,Order_Line,Part
WHERE Sales_Rep.Slsrep_Number = Customer.Slrsrep_Number
AND Customer.C_Number = Orders.C_Number
AND Orders.Order_Number = Order_Line.Order_Number
AND Order_Line.Part_Number = Part.Part_Number
AND Part.Item_Class = 'SG';