SQL 在视图中声明变量

Question

我在下面的 where 语句中创建了一个使用动态变量的视图。

DECLARE 
@wkFileYear SMALLINT = (select fs.FileYear from dbo.FileSemesters fs 
 where fs.systemcurrentflag = 1),
@wkFileSemester SMALLINT = (select fs.FileSemester from dbo.FileSemesters fs where fs.systemcurrentflag = 1)

Select R.FileType, R.FileYear, R.FileSemester, R.ID, R.ClassCode, R1.Raw
from
(
SELECT SC.FileType, SC.FileYear, SC.FileSemester, SC.ID, SC.ClassCode
FROM StudentClasses AS SC 
) as R
LEFT JOIN
(
SELECT  SAR.Filetype,SAR.FileYear, SAR.FileSemester, SAR.ID, SAR.ClassCode, SAR.Result as Raw
FROM    
StudentAssessmentResults AS SAR
) as R1 

on r.FileYear = R1.Fileyear     
and R.FileSemester = R1.FileSemester
and R.FileType = R1.FileType
and R.ClassCode = R1. ClassCode
and R.ID = R1.ID        

where 
R.FileType = 'A'
AND (R.FileYear = @wkFileYear) 
AND (R.FileSemester = 
case 
when (left(R.classcode,2) = '12' or left(R.classcode,2) = '11') and @wkFileSemester = 4 
then 3
else @wkFileSemester
end
)   

我想将此作为视图保存在数据库中，但您不能在视图中声明变量。我查看了有关使用 CTE 或表值函数的所有信息，但完全不确定语法。我尝试使用各种来源的示例创建 CTE 和表值函数，但没有成功。

希望有人能解释我如何仍然可以使用变量，但允许我将其保存为数据库中的视图。

Answer 1

视图的结构依赖于变量是没有意义的。

相反，您需要在视图中创建可以查询的@wkFileYear 和@wkFileSemester 列。

如果您想使用变量，您也可以创建一个 db 函数/存储过程来返回您需要的数据。

这是存储过程的示例。

        CREATE PROCEDURE [dbo].[sp_GetTestData]
            --Param
            @wkFileYear SMALLINT,
            @wkFileSemester SMALLINT
            AS
        BEGIN

        @wkFileYear = select fs.FileYear from dbo.FileSemesters fs where fs.systemcurrentflag = 1
        @wkFileSemester  = select fs.FileSemester from dbo.FileSemesters fs where fs.systemcurrentflag = 1

        Select R.FileType, R.FileYear, R.FileSemester, R.ID, R.ClassCode, R1.Raw
        from
        (
        SELECT SC.FileType, SC.FileYear, SC.FileSemester, SC.ID, SC.ClassCode
        FROM StudentClasses AS SC 
        ) as R
        LEFT JOIN
        (
        SELECT  SAR.Filetype,SAR.FileYear, SAR.FileSemester, SAR.ID, SAR.ClassCode, SAR.Result as Raw
        FROM    
        StudentAssessmentResults AS SAR
        ) as R1 
        on r.FileYear = R1.Fileyear     
        and R.FileSemester = R1.FileSemester
        and R.FileType = R1.FileType
        and R.ClassCode = R1. ClassCode
        and R.ID = R1.ID where 
        R.FileType = 'A'
        AND (R.FileYear = @wkFileYear) 
        AND (R.FileSemester = 
        case 
        when (left(R.classcode,2) = '12' or left(R.classcode,2) = '11') and @wkFileSemester = 4 
        then 3
        else @wkFileSemester
        end
        )
        end