Attempting To Modify Query For Performance...

I've inherited an application that has a query that typically bombs out due to a deadlock in SQL Server 2005. I know where the resource contention is, and why the deadlock happens, and why SQL picks this query to fail, so that's all cool with me. My problem is that I'm in the process of modifying this query to be a little less resource intensive, and I'm getting two different result sets.

The original query is returning 1234 rows, and my first replacement query attempt is returning 930. My replacement query attempt is using a derived table (subquery) rather than copying into a temp table (as the original query is doing). I understand what the missing rows are and why they are not in the result set, so my question is What is it about my replacement query attempt that is so different from the original query?

I appreciate any advice anyone might have to offer.

Best,
B.

/* original query */





Code Block

select * into #response
from response
where MidEndFlag = 'End'

SELECT COUNT(#response.ResponseID) AS TotalCount, CourseInfo.Subject, CourseInfo.Course, CourseInfo.Sect,
CourseInfo.Term, CourseInfo.Enrollment, (COUNT(#response.ResponseID) / (CourseInfo.Enrollment * 1.00))* 100 AS Percentage,
#response.MidEndFlag
FROM #response FULL OUTER JOIN CourseInfo ON #response.Term = CourseInfo.Term AND #response.Subject = CourseInfo.Subject AND
#response.Course = CourseInfo.Course AND #response.Sect = CourseInfo.Sect
WHERE (courseinfo.InstructorSelectionEndFlag = 'Y') and CourseInfo.Enrollment > 0 and courseinfo.term = @term
GROUP BY CourseInfo.Subject, CourseInfo.Course, CourseInfo.Sect, CourseInfo.Term, CourseInfo.Enrollment, #response.MidEndFlag;
/* end original query */

/* my first replacement query attempt */





Code Block

SELECT COUNT(r.ResponseID) AS TotalCount, c.Subject, c.Course, c.Sect, c.Term, c.Enrollment,
(COUNT(r.ResponseID) / (c.Enrollment * 1.00))* 100 AS Percentage, r.MidEndFlag
FROM (select * from dbo.Response where MidEndFlag = 'End') r full outer join CourseInfo as c ON
r.Term = c.Term and r.Subject = c.Subject and r.Course = c.Course and r.Sect = c.Sect
WHERE c.InstructorSelectionEndFlag = 'Y' and c.Enrollment > 0 and c.term = @term and r.MidEndFlag = 'End'
GROUP BY c.Subject, c.Course, c.Sect, c.Term, c.Enrollment, r.MidEndFlag;

/* end my first replacement query attempt */