How to reduce execution time of SQL Select Query - sql

Question

TitemName and TshotName is the problem here
SELECT DISTINCT
tJobs.* ,
tCustomer.Name AS Customer_name ,
(SELECT tEmployee.First + ' ' + tEmployee.Last
FROM tEmployee
WHERE tEmployee.EmployeeID = tJobs.AccountExecutiveID) AS AccountExecutive,
(SELECT tEmployee.First + ' ' + tEmployee.Last
FROM tEmployee
WHERE tEmployee.EmployeeID = tJobs.AccountManagerID) AS AccountManager,
dbo.RetrunUserFavourite(tJobs.JobNumber, 33369, 'Employee') AS Favorites,
(SELECT COUNT(*)
FROM tShots
WHERE tShots.JobNumber = tJobs.JobNumber) AS shotcount,
SUBSTRING((SELECT ', ' + SKU + ', ' + Source + ', ' + ModelNumber
+ ', ' + Description
FROM tItems
WHERE tItems.CustomerID = tCustomer.CustomerID
FOR XML PATH('')), 3, 200000) titemName,
SUBSTRING((SELECT ', ' + ArtDirection + ', '
+ REPLACE(CONVERT(VARCHAR(5), AdDate, 110), '-',
'/')
FROM tShots
WHERE tShots.JobNumber = tJobs.JobNumber
FOR XML PATH('')), 3, 200000) TshotName
FROM
tJobs
INNER JOIN
tCustomer ON tCustomer.CustomerID = tJobs.CustomerID
WHERE
tCustomer.CustomerID = 68666

Answer 1

I strongly agree with M Ali's comments. Two points I would make. The first is not with regard to performance. But, instead of substring() use:
STUFF((SELECT ', ' + SKU + ', ' + Source + ', ' + ModelNumber+ ', ' + Description
FROM tItems
WHERE tItems.CustomerID = tCustomer.CustomerID
FOR XML PATH('')
), 1, 1, '') as titemName
That way, you don't need strange, meaningless numbers floating around the code.
Second, you may need indexes. Based on the highlighted performance problems, I would suggest:
tItems(CustomerID)
and:
tshots(JobNumber, ArtDirection, AdDate)

Answer 2

You have awful lot of string manipulation going on is your query, anyway a slightly improved version of your query would look something like...
Select DISTINCT
tJobs.*
, tCustomer.Name AS Customer_name
, AE.First + ' ' + AE.Last AS AccountExecutive
, AM.First + ' ' + AM.Last AS AccountManager
, dbo.RetrunUserFavourite(tJobs.JobNumber,33369,'Employee')AS Favorites
, TS.shotcount
, SUBSTRING(( SELECT ', ' + SKU + ', ' + Source + ', ' + ModelNumber+ ', ' + Description
FROM tItems
where tItems.CustomerID=tCustomer.CustomerID
FOR XML PATH('')), 3, 200000)titemName
, SUBSTRING(( SELECT ', ' + ArtDirection +', '+REPLACE(CONVERT(VARCHAR(5),AdDate,110), '-','/')
FROM tShots
where tShots.JobNumber=tJobs.JobNumber
FOR XML PATH('')), 3, 200000)TshotName
From tJobs
inner join tCustomer on tCustomer.CustomerID = tJobs.CustomerID
Left join tEmployee AE ON AE.EmployeeID = tJobs.AccountExecutiveID
Left join tEmployee AM ON AM.EmployeeID = tJobs.AccountManagerID
Left join (
SELECT JobNumber , Count(*) shotcount
FROM tShots
GROUP BY JobNumber
) TS ON TS.JobNumber = tJobs.JobNumber
WHERE tCustomer.CustomerID = 68666
A Couple of Pointers:
Having sub-queries in your select statement makes it very inefficient, because the sub-query is executed for each row returned by the outer query, a more sensible way of doing it would be to use joins.
You Also have a call to a User-Defined Scalar function dbo.RetrunUserFavourite() in your select , these scalar UDFs are also performance killers, again the same execution logic is applied here, they are also executed for each row returned by the outer query, a more sensible way would be to put the function logic/code inside a CTE and join your query to that CTE.
These comma delimited lists that you are creating on the fly for last two columns will be slow, maybe an Inline-Table-Valued function can give better performance here.