Question

有关如何解决此查询依赖项问题的任何想法？子查询会有帮助吗？我正在使用的数据库是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]

我所依赖的依赖问题是：

@0 = [table002].[label] //@0 is a string variable

就像尚未创建连接但我需要使用它来创建关系[Grading]的连接。[StudentGradeBucket]或[table028]

Answer 1

这是你正在使用的奇怪的循环连接逻辑，你选择的这些表别名让它更加混乱。别名应该简化，而不是混淆。也就是说，我认为它可以转移到where子句：

...
Left JOIN [Grading].[GradeMark] AS [table022]  ON [table028].[GradeMarkID] = [table022].[GradeMarkID] 
where  @0 = [table002].[label]

如果失败了，你可能需要重新定义你的逻辑......对我来说似乎有点圆。

Answer 2

试试这个：

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]

或者，如果你真的想要左外连接：

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]

或者，如果匹配的GradeBucket记录需要仅返回StudentGradeBucket结果的逻辑;这样：

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
)

SQL多重左连接子查询？

2 个答案: