SQL Query Returning Duplicate Results

Question

Hi,

I've been working out this query now for a while and I thought I had it where I wanted it, but apparently not.

There are two records in the database (orders). The query should return two different rows, but instead returns two rows that have exactly the same values. I think it may be something to do with the GROUP BY or derived tables I'm using but my eyes are tired and not seeing the problem. Can any of you help? Thanks in advance.

SELECT orders.billerID, 
    orders.invoiceDate, 
    orders.txnID, 
    orders.bName, 
    orders.bStreet1, 
    orders.bStreet2, 
    orders.bCity, 
    orders.bState, 
    orders.bZip, 
    orders.bCountry, 
    orders.sName, 
    orders.sStreet1, 
    orders.sStreet2, 
    orders.sCity, 
    orders.sState, 
    orders.sZip, 
    orders.sCountry, 
    orders.paymentType, 
    orders.invoiceNotes, 
    orders.pFee, 
    orders.shipping, 
    orders.tax, 
    orders.reasonCode, 
    orders.txnType, 
    orders.customerID, 
    customers.firstName AS firstName, 
    customers.lastName AS lastName, 
    customers.businessName AS businessName, 
    orderStatus.statusName AS orderStatus, 
    IFNULL(orderItems.itemTotal, 0.00) + orders.shipping + orders.tax AS orderTotal, 
    IFNULL(orderItems.itemTotal, 0.00) + orders.shipping + orders.tax - IFNULL(payments.totalPayments, 0.00) AS orderBalance 
FROM orders 
LEFT JOIN customers ON orders.customerID = customers.id 
LEFT JOIN orderStatus ON orders.orderStatus = orderStatus.id
LEFT JOIN 
    ( 
      SELECT orderItems.orderID, SUM(orderItems.itemPrice * orderItems.itemQuantity) as itemTotal
      FROM orderItems
      GROUP BY orderItems.orderID
    ) orderItems ON orderItems.orderID = orders.id 
LEFT JOIN 
    ( 
      SELECT payments.orderID, SUM(payments.amount) as totalPayments
      FROM payments
      GROUP BY payments.orderID
    ) payments ON payments.orderID = orders.id

Answer 1

When i have this problem i start commenting out one join at a time (and the associated selected columns) until i find the offending join causing the problem.

Answer 2

Typically when you join on many tables and end up with duplicate rows it is because you are not seeing the entire picture. If you were to do a "select *" to see all of the columns included in the query (instead of returning a subset of columns) and compare the resulting rows you would find that somewhere along the way there is a column that contains different data.