Question

I have a database that has been populated with some data using create and insert into statements. I have written a SELECT statement that has a WHERE clause. The problem that I am encountering is that when I run the statement I have found that some of the data is repeating for what reason I don’t understand.

This the statement that I am trying to run.

    SELECT Customer_Contact, Customer.CustomerID, Ord.OrderID,ItemOrdered.BeltLength,ItemOrdered.Colour,
ItemOrdered.Quantity,Design.DesignStyle 
    FROM Customer, Ord, ItemOrdered,Design
    WHERE Customer.CustomerID = Ord.CustomerID
    and Customer.Customer_Contact = 'John Daley' 
and Design.DesignStyle ='Flat-Engraved';

The following link displays all the relevant code, that I have used for to create the above statement. [Database Code][1]

I have laid it out in the following format:

CREATE STATEMENT 
INSERT INTO STATEMENT 

Expanded Where clause and looks like the following:

SELECT Customer_Contact, Customer.CustomerID, Ord.OrderID,ItemOrdered.BeltLength,ItemOrdered.Colour,
ItemOrdered.Quantity,Design.DesignStyle 
FROM Customer, Ord, ItemOrdered,Design
WHERE Customer.CustomerID = Ord.CustomerID and 
ItemOrdered.OrderID = Ord.OrderID
and Customer.Customer_Contact = 'John Daley' and 
Design.DesignStyle ='Flat-Engraved';

This works, however when I run the statement it brings up 3 records that are exactly the same.

SELECT Customer.Customer_Contact, 
       Customer.CustomerID, 
       Ord.OrderID,
       ItemOrdered.BeltLength,
       ItemOrdered.Colour,
       ItemOrdered.Quantity,
       Design.DesignStyle
  FROM Customer,
       Ord, 
       ItemOrdered,
       BeltID
       Design
 WHERE Customer.CustomerID       = Ord.CustomerID
   AND Ord.OrderID               = ItemOrdered.OrderID
   AND Customer.Customer_Contact = 'John Daley' 
   AND Design.DesignStyle        ='Flat-Engraved'
   AND BeltID.DesignID           = Design.DesignID;

The above statement is giving me an invalid identifier error, which I seem to not understand why?

Answer 1

It seems like you want to select something from the Design and ItemOrdered tables, but you are not including them in your join.

You probably need to expand your where-clause (with and-statements), where you link the ItemOrdered and Design tables to your Customer or Customer_Contract tables.