SQL query that uses a GROUP BY and IN is too slow - sql

Question

I am struggling to speed this SQL query up. I have tried removing all the fields besides the two SUM() functions and the Id field but it is still incredibly slow. It is currently taking 15 seconds to run. Does anyone have any suggestions to speed this up as it is currently causing a timeout on a page in my web app. I need the fields shown so I can't really remove them but there surely has to be a way to improve this?
SELECT [Customer].[iCustomerID],
[Customer].[sCustomerSageCode],
[Customer].[sCustomerName],
[Customer].[sCustomerTelNo1],
SUM([InvoiceItem].[fQtyOrdered]) AS [Quantity],
SUM([InvoiceItem].[fNetAmount]) AS [Value]
FROM [dbo].[Customer]
LEFT JOIN [dbo].[CustomerAccountStatus] ON ([Customer].[iAccountStatusID] = [CustomerAccountStatus].[iAccountStatusID])
LEFT JOIN [dbo].[SalesOrder] ON ([SalesOrder].[iCustomerID] = [dbo].[Customer].[iCustomerID])
LEFT JOIN [Invoice] ON ([Invoice].[iCustomerID] = [Customer].[iCustomerID])
LEFT JOIN [dbo].[InvoiceItem] ON ([Invoice].[iInvoiceNumber] = [InvoiceItem].[iInvoiceNumber])
WHERE ([InvoiceItem].[sNominalCode] IN ('4000', '4001', '4002', '4004', '4005', '4006', '4007', '4010', '4015', '4016', '700000', '701001', '701002', '701003'))
AND( ([dbo].[SalesOrder].[dOrderDateTime] >= '2013-01-01')
OR ([dbo].[Customer].[dDateCreated] >= '2014-01-01'))
GROUP BY [Customer].[iCustomerID],[Customer].[sCustomerSageCode],[Customer].[sCustomerName], [Customer].[sCustomerTelNo1];

Answer 1

I don't think this query is doing what you want anyway. As written, there are no relationships between the Invoice table and the SalesOrder table. This leads me to believe that it is producing a cartesian product between invoices and orders, so customers with lots of orders would be generating lots of unnecessary intermediate rows.
You can test this by removing the SalesOrder table from the query:
SELECT c.[iCustomerID], c.[sCustomerSageCode], c.[sCustomerName], c.[sCustomerTelNo1],
SUM(it.[fQtyOrdered]) AS [Quantity], SUM(it.[fNetAmount]) AS [Value]
FROM [dbo].[Customer] c LEFT JOIN
[dbo].[CustomerAccountStatus] cas
ON c.[iAccountStatusID] = cas.[iAccountStatusID] LEFT JOIN
[Invoice] i
ON (i.[iCustomerID] = c.[iCustomerID]) LEFT JOIN
[dbo].[InvoiceItem] it
ON (i.[iInvoiceNumber] = it.[iInvoiceNumber])
WHERE it.[sNominalCode] IN ('4000', '4001', '4002', '4004', '4005', '4006', '4007', '4010', '4015', '4016', '700000', '701001', '701002', '701003') AND
c.[dDateCreated] >= '2014-01-01'
GROUP BY c.[iCustomerID], c.[sCustomerSageCode], c.[sCustomerName], c.[sCustomerTelNo1];
If this works and you need the SalesOrder, then you will need to either pre-aggregate by SalesOrder or find better join keys.
The above query could benefit from an index on Customer(dDateCreated, CustomerId).

Answer 2

You have a lot of LEFT JOIN
I don't see CustomerAccountStatus usage. Ou can exclude it
The [InvoiceItem].[sNominalCode] could be null in case of LEFT JOIN so add [InvoiceItem].[sNominalCode] is not null or <THE IN CONDITION>
Also add the is not null checks to other conditions

Answer 3

It seems you are looking for customers that are either created this year or for which sales orders exist from last year or this year. So select from customers, but use EXISTS on SalesOrder. Then you want to count invoices. So outer join them and make sure to have the criteria in the ON clause. (sNominalCode will be NULL for any outer joined records. Hence asking for certain sNominalCode in the WHERE clause will turn your outer join into an inner join.)
SELECT
c.iCustomerID,
c.sCustomerSageCode,
c.sCustomerName,
c.sCustomerTelNo1,
SUM(ii.fQtyOrdered) AS Quantity,
SUM(ii.fNetAmount) AS Value
FROM dbo.Customer c
LEFT JOIN dbo.Invoice i ON (i.iCustomerID = c.iCustomerID)
LEFT JOIN dbo.InvoiceItem ii ON (ii.iInvoiceNumber = i.iInvoiceNumber AND ii.sNominalCode IN ('4000', '4001', '4002', '4004', '4005', '4006', '4007', '4010', '4015', '4016', '700000', '701001', '701002', '701003'))
WHERE c.dDateCreated >= '2014-01-01'
OR EXISTS
(
SELECT *
FROM dbo.SalesOrder
WHERE iCustomerID = c.iCustomerID
AND dOrderDateTime >= '2013-01-01'
)
GROUP BY c.iCustomerID, c.sCustomerSageCode, c.sCustomerName, c.sCustomerTelNo1;