SQL query is loading for long period, how it could be optimized? - sql

Question

This is the query:
SELECT
[Code]
FROM (
SELECT
ROW_NUMBER() OVER (PARTITION BY [OrderNo], [ProductNo] ORDER BY [Quantity] DESC) AS [RowNumber],
SUBSTRING(P.[ProductNo], 1, 2) AS [Code]
FROM [LESMESPRD].[FlexNet_prd].[dbo].[ORDER_DETAIL] AS OD
INNER JOIN [LESMESPRD].[FlexNet_prd].[dbo].[WIP_COMPONENT] AS WC ON [WC].[WiporderNo] = OD.[OrderNo]
AND WC.[WipOrderType] = OD.[OrderType]
AND WC.[Active] = 1
INNER JOIN [LESMESPRD].[FlexNet_prd].[dbo].[COMPONENT] AS C ON C.[ID] = WC.[ComponentID]
INNER JOIN [LESMESPRD].[FlexNet_prd].[dbo].[PRODUCT] AS P ON P.[ID] = C.[ProductID]
WHERE SUBSTRING(P.[ProductNo], 1, 2) IN ('43', '72')
) AS OrderBrandComponents
WHERE [RowNumber] = 1
Executing time is 1 minute and 16 seconds, maybe you can help me optimize it somehow? This query is just small piece of the code, but I found that exactly this part is slowing the process.
I tried to think that maybe problem is in sub select when I try to get my rownumber, from these tables that are linked servers data is executing in seconds, I think problem is with the functions. I hope that this query could be optimized.

Answer 1

I believe the delay is because your query is not sargable based on the SUBSTRING( P.[ProductNo], 1,2 ). The engine can not utilize an index on a function call. But by using the full column and using LIKE based on the first 2 characters Plus wild-card anything after, you get the same records, but able to use an index.
Now, because you are looking for 2 specific product type codes (43 and 72), I reversed the query to START with that table, then find orders the products were used. This may help optimize speed, especially if you have 100 orders with these products, but 1000s of orders otherwise. Thus, starting with a smaller set to begin with.
Also, you dont need all the square brackets all over. Typically, those are only used if you have a column name based on a "reserved" keyword, such as naming a column "from" which is an obvious keyword in a SQL statement. Or things that are known data types, function names, etc.
Finally indexes to help optimize this. I would ensure you have indexes on the following tables
table index
Product ( ProductNo, Id ) -- specifically this order
Component ( ProductID, Id
WIP_COMPONENT ( ComponentId, Active, WipOrderNo, WipOrderType )
ORDER_DETAIL ( OrderNo, OrderType )
SELECT
Code
FROM
(SELECT
ROW_NUMBER() OVER
(PARTITION BY OrderNo, ProductNo
ORDER BY Quantity DESC) AS RowNumber,
SUBSTRING(P.ProductNo, 1, 2) Code
FROM
LESMESPRD.FlexNet_prd.dbo.PRODUCT P
JOIN LESMESPRD.FlexNet_prd.dbo.COMPONENT C
ON P.ID = C.ProductID
JOIN LESMESPRD.FlexNet_prd.dbo.WIP_COMPONENT WC
ON C.ID = WC.ComponentID
AND WC.Active = 1
JOIN LESMESPRD.FlexNet_prd.dbo.ORDER_DETAIL OD
ON WC.WiporderNo = OD.OrderNo
AND WC.WipOrderType = OD.OrderType
WHERE
P.ProductNo like '43%'
OR P.ProductNo like '72%' ) AS OrderBrandComponents
WHERE
OrderBrandComponents.RowNumber = 1