Optimized query for a subquery in sql - sql

Question

I made a query to get the inventory of products as follows:
Select
b.ProductID, c.ProductName,
(Select
Case
When SUM(Qty) IS NULL
then 0
else SUM(Qty)
end
from
InvoiceDetails
where
ProductID = b.ProductID) as Sold,
(Select
Case
When SUM(QtyReceive) IS NULL
then 0
else SUM(QtyReceive)
end
from
PurchaseOrderDetails
where
ProductID = b.ProductID) as Stocks,
((Select
Case
When SUM(QtyReceive) IS NULL
then 0
else SUM(QtyReceive)
end
from
PurchaseOrderDetails
where
ProductID = b.ProductID) -
(Select
Case
When SUM(Qty) IS NULL
then 0
else SUM(Qty)
end
from
InvoiceDetails
where
ProductID = b.ProductID)) as RemainingStock
from
InvoiceDetails a
Right join
PurchaseOrderDetails b on a.ProductID = b.ProductID
Inner join
Products c on b.ProductID = c.ProductID
Group By
b.ProductID, c.ProductName
This query returns the data that I want, and it runs fine in my desktop, but when I deploy the application that runs this query on a lower specs laptop, it is really slow and causes the laptop to hang. I need some help on how to optimize the query or maybe change it to make it more efficient... thanks in advance
This are the data of my InvoiceDetails table
Data From my PurchaseOrderDetails table
Data from Products table

Answer 1

So I've taken out your subqueries in the select, I don't think these were necessary at all. I've also moved around your joins and given better aliases to the tables;
SELECT
b.ProductID,
c.ProductName,
ISNULL(SUM(id.Qty),0) as Sold,
ISNULL(SUM(pod.QtyReceive),0) as Stocks,
ISNULL(SUM(pod.QtyReceive),0) - ISNULL(SUM(id.Qty),0) as RemainingStock
FROM PurchaseOrderDetails pod
INNER JOIN Products pr
ON pr.ProductID = pod.ProductID
LEFT JOIN InvoiceDetails id
ON id.ProductID = pod.ProductID
GROUP BY
pod.ProductID, pr.ProductName
You were already joining those two tables so you don't need subqueries in the select at all. I've also wrapped the SUM in ISNULL to ensure there are no NULL errors.
I'd suggest using the SET STATISTICS TIME,IO ON at the beginning of your code (with an OFF command at the end). Then copy all of the text from your 'messages' tab into statisticsparser.com. Do this for both queries and compare, check the total CPU time and the logical reads, you want these both lower for better performance. I'm betting your logical reads will drop significantly with this new query.
EDIT
OK, I've put together a new query based upon your sample data. I've only used the fields that we actually need for this query so that it's simpler for this example.
Sample Data
CREATE TABLE #InvoiceDetails (ProductID int, Qty int)
INSERT INTO #InvoiceDetails (ProductID,Qty)
VALUES (3,50),(1,0),(2,1),(1,12),(2,1),(3,1),(1,1),(2,1),(1,1),(2,1)
CREATE TABLE #PurchaseOrderDetails (ProductID int, Qty int)
INSERT INTO #PurchaseOrderDetails (ProductID, Qty)
VALUES (1,100),(2,20),(4,10),(1,12),(5,12),(4,12),(3,12),(2,20),(3,20),(4,20),(5,20)
CREATE TABLE #Products (ProductID int, ProductName varchar(20))
INSERT INTO #Products (ProductID, ProductName)
VALUES (1,'Sample Product'),(2,'DYE INK CYAN'),(3,'test Product 1'),(4,'test Product 2'),(5,'test Product 3'),(1004,'TESTING PRODUCT')
For this, here is the output of your original query
ProductID ProductName Sold Stocks RemainingStock
1 Sample Product 14 112 98
2 DYE INK CYAN 4 40 36
3 test Product 1 51 32 -19
4 test Product 2 0 42 42
5 test Product 3 0 32 32
This is the re-written query that I've used. Note, there are no subqueries within the SELECT statement, they're within the joins as they should be. Also see that as we're aggregating in the subqueries we don't need to do this in the outer query too.
SELECT
pod.ProductID,
pr.ProductName,
ISNULL(id.Qty,0) as Sold,
ISNULL(pod.Qty,0) as Stocks,
ISNULL(pod.Qty,0) - ISNULL(id.Qty,0) as RemainingStock
FROM #Products pr
INNER JOIN (SELECT ProductID, SUM(Qty) Qty FROM #PurchaseOrderDetails GROUP BY ProductID) pod
ON pr.ProductID = pod.ProductID
LEFT JOIN (SELECT ProductID, SUM(Qty) Qty FROM #InvoiceDetails GROUP BY ProductID) id
ON id.ProductID = pr.ProductID
And this is the new output
ProductID ProductName Sold Stocks RemainingStock
1 Sample Product 14 112 98
2 DYE INK CYAN 4 40 36
3 test Product 1 51 32 -19
4 test Product 2 0 42 42
5 test Product 3 0 32 32
Which matches your original query.
I'd suggest trying this query on your machines and seeing which performs better, try the STATISTICS TIME,IO command I mentioned previously.

Answer 2

You grouped by b.ProductID, c.ProductName then you could use aggregate function to calculate.
And create indexes in your table to improve performance.
Select
b.ProductID, c.ProductName,
SUM(isnull(a.Qty,0)) as Sold,
SUM(b.QtyReceive) as Stocks,
SUM(b.QtyReceive) - SUM(isnull(a.Qty,0)) as RemainingStock
from
PurchaseOrderDetails b
LEFT JOIN InvoiceDetails a on a.ProductID = b.ProductID
INNER JOIN Products c on b.ProductID = c.ProductID
Group By
b.ProductID, c.ProductName

Answer 3

Can you try this? (I wrote without testing, as you didn't post sample data nor create table). Please check it and use as a starting point. Compare results from your query and this and compare execution plan. Analysis of performances requires "some" knowledge of Sql and ability to consider several things (eg. how many rows, are there indexes, using of execution plan and statistics, etc.)
SELECT C.PRODUCTID
,C.PRODUCTNAME
,COALESCE(D.QTY_SOLD,0) AS QTY_SOLD
,COALESCE(E.QTY_STOCKS,0) AS QTY_STOCKS
,COALESCE(E.QTY_STOCKS,0)-COALESCE(D.QTY_SOLD,0) AS REMAININGSTOCK
FROM PRODUCTS C
LEFT JOIN (SELECT PRODUCTID, SUM(QTY) AS QTY_SOLD
FROM INVOICEDETAILS
GROUP BY PRODUCTID
) D ON B.PRODUCTID = D.PRODUCTID
LEFT JOIN (SELECT PRODUCTID,SUM(QTYRECEIVE) AS QTY_STOCKS
FROM PURCHASEORDERDETAILS
GROUP BY PRODUCTID
) E ON B.PRODUCTID = E.PRODUCTID

Answer 4

Looking to your query, I think this could be equivalent (or at least I hope it is):
Select
b.ProductID
, c.ProductName
, Case When SUM(a.Qty) IS NULL then 0 else SUM(a.Qty) end as sold
, Case When SUM(b.QtyReceive) IS NULL then 0 else SUM(b.QtyReceive) end as Stock
, Case When SUM(isnull(a.Qty,0 ) - isnull(b.QtyReceive,0)) IS NULL
then 0
else SUM(isnull(a.Qty,0 ) - isnull(b.QtyReceive,0)) end as RemainingStock
from Products c
left join InvoiceDetails a on c.ProductID = a.ProductID
left join PurchaseOrderDetails b on c.ProductID = b.ProductID
Group By b.ProductID,c.ProductName