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SQL query

I need ti improve the sql performance

SELECT COUNT(*) as totalCnt,
	SUM(CASE WHEN IR.sessionType = 1 THEN 1 END) BTWRatingCount,
	SUM(CASE WHEN IR.sessionType = 0 THEN 1 END) ClassRatingCount,
	CONVERT(DECIMAL(10, 2),AVG(IRQA.btwAvgRating)) btwAvgRating,
	CONVERT(DECIMAL(10, 2),AVG(IRQA.classAvgRating)) classAvgRating,
	CONVERT(DECIMAL(10, 2),IRQTotal.overallAvgRating) overallAvgRating
FROM dbo.instructorRating IR
CROSS APPLY (SELECT AVG(CASE WHEN IR2.sessionType = 1 THEN CAST(IRQ.scaleID AS FLOAT) ELSE NULL END) as btwAvgRating,
                    AVG(CASE WHEN IR2.sessionType = 0 THEN CAST(IRQ.scaleID AS FLOAT) ELSE NULL END) as classAvgRating
             FROM dbo.instructor_rating_question IRQ
			 INNER JOIN dbo.instructorRating IR2 ON IR2.ratingID = IRQ.ratingID
			 WHERE IR2.sessionUnitKey = IR.sessionUnitKey) IRQA
CROSS JOIN (SELECT AVG(CAST(IRQ.scaleID AS FLOAT)) overallAvgRating
			FROM dbo.instructor_rating_question IRQ
			INNER JOIN dbo.instructorRating IR ON IR.ratingID = IRQ.ratingID) IRQTotal
GROUP BY IRQTotal.overallAvgRating

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0
erikTsomik
Asked:
erikTsomik
  • 2
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1 Solution
 
PortletPaulCommented:
Does this inner join approach make any/much difference?
SELECT
      COUNT(*)                                           AS totalCnt
    , SUM(CASE WHEN IR.sessionType = 1 THEN 1 END)       BTWRatingCount
    , SUM(CASE WHEN IR.sessionType = 0 THEN 1 END)       ClassRatingCount
    , CONVERT(decimal(10, 2), AVG(IRQA.btwAvgRating))    btwAvgRating
    , CONVERT(decimal(10, 2), AVG(IRQA.classAvgRating))  classAvgRating
    , CONVERT(decimal(10, 2), IRQTotal.overallAvgRating) overallAvgRating
FROM dbo.instructorRating IR
INNER JOIN (
      SELECT
            IRQ.ratingID
          , AVG(CASE WHEN IR2.sessionType = 1 THEN CAST(IRQ.scaleID AS float) ELSE NULL END) AS btwAvgRating
          , AVG(CASE WHEN IR2.sessionType = 0 THEN CAST(IRQ.scaleID AS float) ELSE NULL END) AS classAvgRating
      FROM dbo.instructor_rating_question IRQ
      INNER JOIN dbo.instructorRating IR2 ON IR2.ratingID = IRQ.ratingID
      GROUP BY
            IRQ.ratingID
) IRQA ON IR.ratingID = IRQA.ratingID
CROSS JOIN (
      SELECT
            AVG(CAST(IRQ.scaleID AS float)) overallAvgRating
      FROM dbo.instructor_rating_question IRQ
      INNER JOIN dbo.instructorRating IR ON IR.ratingID = IRQ.ratingID
) IRQTotal
GROUP BY
      IRQTotal.overallAvgRating

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can you provide the execution plan please? (attach as a .sqlplan file)
0
 
Pawan KumarDatabase ExpertCommented:
Here is the fix., Please try..

SELECT COUNT(*) as totalCnt,
	SUM(CASE WHEN IR.sessionType = 1 THEN 1 END) BTWRatingCount,
	SUM(CASE WHEN IR.sessionType = 0 THEN 1 END) ClassRatingCount,
	CONVERT(DECIMAL(10, 2),AVG(IRQA.btwAvgRating)) btwAvgRating,
	CONVERT(DECIMAL(10, 2),AVG(IRQA.classAvgRating)) classAvgRating,
	CONVERT(DECIMAL(10, 2),IRQTotal.overallAvgRating) overallAvgRating
FROM dbo.instructorRating IR
CROSS APPLY (SELECT AVG(CASE WHEN IR.sessionType = 1 THEN (IRQ.scaleID) * 1. ELSE NULL END) as btwAvgRating,
                    AVG(CASE WHEN IR.sessionType = 0 THEN (IRQ.scaleID) * 1. ELSE NULL END) as classAvgRating
             FROM dbo.instructor_rating_question IRQ			 
			 WHERE IR.sessionUnitKey = IR.sessionUnitKey) IRQA
CROSS APPLY (SELECT AVG(CAST(IRQ.scaleID AS FLOAT)) overallAvgRating
			FROM dbo.instructor_rating_question IRQ
			WHERE IR.ratingID = IRQ.ratingID) IRQTotal
GROUP BY IRQTotal.overallAvgRating

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0
 
PortletPaulCommented:
"here is THE fix"

Really? No other approach would be needed or appropriate?
How can you be so certain ....... when you don't even know what the indexes are?

How does changing a cross join (of a single value) to a cross apply assist overall performance?
0
 
Pawan KumarDatabase ExpertCommented:
Yes I think this will improve the performance. I changed other things also. Please check again.
0

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