存储过程：使用动态 SQL 进行数据透视时传递参数

Question

正如标题所示，我正在尝试使用动态 SQL 来获取透视表的列名 - 但是，我也希望能够将参数传递给名为 @assessments 的变量，但我似乎无法让它工作。以下是我正在使用的代码，如果有人可以看一下并让我知道我哪里出错了，我将不胜感激。谢谢

    create PROCEDURE [dbo].[spTestExamResults]

    AS
    BEGIN

        DECLARE @SQL as NVARCHAR(MAX)
        DECLARE @ColumnName as NVARCHAR(MAX)
        DECLARE @assessment as NVARCHAR(50)

        SET NOCOUNT ON;

    --Get distinct values from pivot source

    SELECT @ColumnName = ISNULL(@ColumnName + ',','') + QUOTENAME(subjectname)

    From (SELECT DISTINCT SubjectName From qryPupilNCTest) as p order by p.Subjectname

    SET @SQL = 
    'select pupil,PupilName, year' + @ColumnName + '
    FROM qrypupilnctest
    Where assessment in (' + @assessment + ')
    PIVOT (MAX(grade) for subjectname in (' +@ColumnName + ')) piv'


    EXEC (@SQL)

    END

Answer 1

在您的情况下，@assessment 是没有任何初始化并在操作中处理的局部变量。所以它总是只有空值，你不会从存储过程中得到任何结果。

根据您的帖子标题，您可以更改存储过程并将@assessment 作为参数传递，因此WHERE assessment IN ( 将包含一些有效数据并且您将收到一些有效结果。

ALTER PROCEDURE [dbo].[spTestExamResults]
(
  @assessment   NVARCHAR(50)
)
AS
BEGIN

    DECLARE @SQL AS NVARCHAR(MAX)
    DECLARE @ColumnName AS NVARCHAR(MAX)
    -- DECLARE @assessment as NVARCHAR(50)  -- Remove the @assessment from the local variable 

    SET NOCOUNT ON;

    --Get distinct values from pivot source
    SELECT @ColumnName = ISNULL(@ColumnName + ',','') + QUOTENAME(subjectname)
    FROM (SELECT DISTINCT SubjectName FROM qryPupilNCTest) AS p 
    ORDER BY p.Subjectname

    SET @SQL = 'SELECT pupil, PupilName, year' + @ColumnName + '
    FROM qrypupilnctest
    WHERE assessment IN (' + @assessment + ')
    PIVOT (MAX(grade) FOR subjectname IN (' + @ColumnName + ')) piv'

    EXEC (@SQL)

END

所以执行调用将是：

EXEC [dbo].[spTestExamResults] 'paramvalue1, paramvalue2'