One Big Query Or Use Temporary Table?

Hi,

Can any of you tell me what is right?

When we are writing a big query that against to 25+ tables (it has lots of lookup and lots of business logic in it so it will have lots of left outer joins, right outer joins, inner join, UNION, group by, and lots of SQL server functions) should we put everything in one select statement? Or we should create lots of temporary tables and then join them together?

My friend told me that I should use one statement instead of lots of temp tables in order to reduce the physical read. He does not like the temp table idea since there will be lots of user running the query in the same time and it will use lots of space. But I don’t believe that is true. (I believe when you put everything in one statement, SQL server still needs to create the result set in the temp db.) There will be lots of join going on and it could hurt the performance.

I believe that
1.We should create the temp tables and then join the temp tables together later to get the final results. we can create the index on the temp table at runtime.
2.If the order of columns in the index does not match to our where clause, then the index is useless.
3.If there is a SQL function in the where clause, the index is useless. (for example, where Datepart(yy, orderdate)=’1998’)
4.If there is a NOT in the where clause, the index is useless.

What do you think? Are you agree with me?

Following is the query. Is there any better way to do this?

Select d.Description as Division,
c.Description as Region,
b.StateCode as State,
b.FacilityNumber,
b.Name as FacilityName,
(Case When a.ExitDate Is Not Null Then Convert(Varchar(10),a.ExitDate,101)
Else 'Pending' End) as PriorStdSurveyExit,
(Case When a.ExitDate Is Not Null And a.IJValid > 0
Then Convert(Varchar(10),a.ExitDate+89,101)
Else '' End) as ThreeMonthWindow,
(Case When a.ExitDate Is Not Null Then Convert(Varchar(10),a.ExitDate+179,101)
When a.IJValid > 0 Then Convert(Varchar(10),a.ExitDate+179,101)
Else 'Pending' End) as SixMonthWindow,
(Case When a.ExitDate Is Not Null Then Convert(Varchar(10),a.ExitDate+450,101)
When a.IJValid > 0 Then Convert(Varchar(10),a.ExitDate+450,101)
Else 'Pending' End) as FifteenMonthWindow
From (
Select a.FacilityNumber, a.ExitDate, IsNull(b.FacilityNumber,0) as IJValid
From
(
Select b.FacilityNumber, Max(a.ExitDate) as ExitDate
From Survey a
Inner Join Facility b on (a.FacilityID = b.FacilityID)
Inner Join SurveyFormatCode c on (a.SurveyFormatCodeID = c.SurveyFormatCodeID)
Inner Join SurveyTypeCode d on (a.SurveyTypeCodeID = d.SurveyTypeCodeID)
Where a.VerbalResultDate is Not Null
And c.Description Like 'Standard%'
And d.Description Like 'LTC%'
And a.ExitDate <= @InDate
Group By b.FacilityNumber
) a Left Join
(
Select Distinct b.FacilityNumber
From Survey a
Inner Join Facility b on (a.FacilityID = b.FacilityID)
Inner Join SurveyFormatCode c on (a.SurveyFormatCodeID = c.SurveyFormatCodeID)
Inner Join SurveyTypeCode d on (a.SurveyTypeCodeID = d.SurveyTypeCodeID)
Inner Join ComplianceRatingCode e on (a.ComplianceRatingCodeID = e.ComplianceRatingCodeID)
Where a.VerbalResultDate is Not Null
And (c.Description Like 'Standard%'
And d.Description Like 'LTC%')
And e.Description Like 'Category 4%'
And a.ExitDate <= @InDate
Union
Select Distinct b.FacilityNumber
From (
Select b.FacilityNumber, Max(a.ExitDate) as ExitDate
From SurveyCitation e
Inner Join Survey a on (a.SurveyID = e.SurveyID)
Inner Join Facility b on (a.FacilityID = b.FacilityID)
Inner Join SurveyFormatCode c on (a.SurveyFormatCodeID = c.SurveyFormatCodeID)
Inner Join SurveyTypeCode d on (a.SurveyTypeCodeID = d.SurveyTypeCodeID)
Inner Join Citation f on (e.CitationID = f.CitationID)
Inner Join SSLetterCode g on (f.SSLetterCodeID = g.SSLetterCodeID)
Where a.VerbalResultDate is Not Null
And d.Description Like 'LTC%'
And a.ExitDate <= @InDate
And g.SSLetterCode in ('J','K','L')
Group By b.FacilityNumber
) a
Right Join
(
Select b.FacilityNumber, Max(a.ExitDate) as ExitDate
From SurveyCitation e
Inner Join Survey a on (a.SurveyID = e.SurveyID)
Inner Join Facility b on (a.FacilityID = b.FacilityID)
Inner Join SurveyFormatCode c on (a.SurveyFormatCodeID = c.SurveyFormatCodeID)
Inner Join SurveyTypeCode d on (a.SurveyTypeCodeID = d.SurveyTypeCodeID)
Where a.VerbalResultDate is Not Null
And c.Description Like 'Standard%'
And d.Description Like 'LTC%'
And a.ExitDate <= @InDate
Group By b.FacilityNumber

) b on (a.FacilityNumber = b.FacilityNumber)
Where a.ExitDate >= b.ExitDate

) b on (a.FacilityNumber = b.FacilityNumber)
) a Right Join Facility b on (a.FacilityNumber = b.FacilityNumber)
Left Join Region c on (b.RegionID = c.RegionID)
Left Join Division d on (c.DivisionID = d.DivisionID)
Order By d.Description, c.Description, b.FacilityNumber