SQL multiple left join in subquery? - sql

Question

Any idea on how to resolve this query dependency issue? Would subquery help? Database I'm using is sql server 2012.
FROM [Scheduling].[studentsection] AS [table027]
Left JOIN [Grading].[StudentGradeBucket] AS [table028]
ON ([table028].[StudentSectionID] = [table027].[StudentSectionID])
And (#0 = [table002].[label])
Left JOIN [Grading].[GradingPeriodGradeBucket] AS [table029]
ON [table028].[GradingPeriodGradeBucketID] = [table029].[GradingPeriodGradeBucketID]
Left JOIN [Grading].[GradeBucket] AS [table002]
ON [table029].[GradeBucketID] = [table002].[GradeBucketID]
Left JOIN [Grading].[GradeBucketType] AS [table001]
ON [table002].[GradeBucketTypeID] = [table001].[GradeBucketTypeID]
Left JOIN [Grading].[GradeMark] AS [table022]
ON [table028].[GradeMarkID] = [table022].[GradeMarkID]
The dependency issue I have is with this:
#0 = [table002].[label] //#0 is a string variable
Like the join hasn't been created yet but I need to use it to create the join for relationship [Grading].[StudentGradeBucket] or [table028]

Answer 1

That is weird circular join logic you are using and these table alias's you have chosen are making it more confusing. Alias's should simplify, not confuse. That said, I think it can just be moved to the where clause:
...
Left JOIN [Grading].[GradeMark] AS [table022] ON [table028].[GradeMarkID] = [table022].[GradeMarkID]
where #0 = [table002].[label]
If that fails, you may need to redefine your logic...it seems a bit circular to me.

Answer 2

Try this:
declare #0 nvarchar(max) = 'label value'
select *
from [Scheduling].[studentsection] as ss
left join [Grading].[StudentGradeBucket] as sgb
on sgb.[StudentSectionID] = ss.[StudentSectionID]
inner join [Grading].[GradingPeriodGradeBucket] as gpgb
on gpgb.[GradingPeriodGradeBucketID] = sgb.[GradingPeriodGradeBucketID]
inner join [Grading].[GradeBucket] as gb
on gb.[GradeBucketID] = gpgb.[GradeBucketID]
and gb.[label] = #0
left join [Grading].[GradeBucketType] as gbt
on gbt.[GradeBucketTypeID] = gb.[GradeBucketTypeID]
left join [Grading].[GradeMark] as gm
on gm.[GradeMarkID] = sgb.[GradeMarkID]
Or this if you really want left outer joins:
declare #0 nvarchar(max) = 'label value'
select *
from [Scheduling].[studentsection] as ss
left join [Grading].[StudentGradeBucket] as sgb
on sgb.[StudentSectionID] = ss.[StudentSectionID]
left join [Grading].[GradingPeriodGradeBucket] as gpgb
on gpgb.[GradingPeriodGradeBucketID] = sgb.[GradingPeriodGradeBucketID]
left join [Grading].[GradeBucket] as gb
on gb.[GradeBucketID] = gpgb.[GradeBucketID]
and gb.[label] = #0
left join [Grading].[GradeBucketType] as gbt
on gbt.[GradeBucketTypeID] = gb.[GradeBucketTypeID]
left join [Grading].[GradeMark] as gm
on gm.[GradeMarkID] = sgb.[GradeMarkID]
Or if you need the logic of only returning results from the StudentGradeBucket when there's a matching GradeBucket record; this:
declare #0 nvarchar(max) = 'label value'
select *
from [Scheduling].[studentsection] as ss
left join [Grading].[StudentGradeBucket] as sgb
on sgb.[StudentSectionID] = ss.[StudentSectionID]
left join [Grading].[GradingPeriodGradeBucket] as gpgb
on gpgb.[GradingPeriodGradeBucketID] = sgb.[GradingPeriodGradeBucketID]
left join [Grading].[GradeBucket] as gb
on gb.[GradeBucketID] = gpgb.[GradeBucketID]
left join [Grading].[GradeBucketType] as gbt
on gbt.[GradeBucketTypeID] = gb.[GradeBucketTypeID]
left join [Grading].[GradeMark] as gm
on gm.[GradeMarkID] = sgb.[GradeMarkID]
where
( --filter on the gb label only if there's a result from the sgb table;
sgb.[StudentSectionID] is null
or and gb.[label] = #0
)