Question

我正在进行一个长查询，这是其中的一部分：

SELECT '3' AS RowType
    ,DTH.EnteredBy AS Person
    ,COALESCE(PDT.[Name], APP.AppName) AS Project
    ,(
        CASE WHEN (
                    STY.KanBanProductId IS NOT NULL
                    AND STY.SprintId IS NULL
                    ) THEN 'Kanban' WHEN (
                    STY.KanBanProductId IS NULL
                    AND STY.SprintId IS NOT NULL
                    ) THEN 'Sprint' ELSE SCY.Catagory END
        ) AS ProjectType
    ,dbo.primaryTheme(STY.[Number], ???) AS Theme

哪里???是的，我遇到了问题。

我需要传递上一列的结果，即：

CASE WHEN (
                        STY.KanBanProductId IS NOT NULL
                        AND STY.SprintId IS NULL
                        ) THEN 'Kanban' WHEN (
                        STY.KanBanProductId IS NULL
                        AND STY.SprintId IS NOT NULL
                        ) THEN 'Sprint' ELSE SCY.Catagory END
            )

实现这一目标的最佳方法是什么？

Answer 1

您可以重复查询，只执行一次，或者您可以使用子查询/ CTE：

WITH CTE AS
(
    SELECT '3' AS RowType
    ,DTH.EnteredBy AS Person
    ,COALESCE(PDT.[Name], APP.AppName) AS Project
    ,(
        CASE WHEN (
                    STY.KanBanProductId IS NOT NULL
                    AND STY.SprintId IS NULL
                    ) THEN 'Kanban' WHEN (
                    STY.KanBanProductId IS NULL
                    AND STY.SprintId IS NOT NULL
                    ) THEN 'Sprint' ELSE SCY.Catagory END
        ) AS ProjectType
    FROM dbo.TableName
)
SELECT *, Theme = dbo.primaryTheme(Number, ProjectType)
FROM CTE

Answer 2

您可以使用“Cross Apply”或CTE（Common Table Expression）来执行此操作。我更喜欢Cross Apply，所以这里有一个例子：

SELECT '3' AS RowType
    ,DTH.EnteredBy AS Person
    ,COALESCE(PDT.[Name], APP.AppName) AS Project
    ,CAResult.ProjectType
    ,dbo.primaryTheme(STY.[Number], CAResult.ProjectType) AS Theme
FROM [SomeTable]
CROSS APPLY (SELECT CASE WHEN (
                    KanBanProductId IS NOT NULL
                    AND SprintId IS NULL
                    ) THEN 'Kanban' WHEN (
                    KanBanProductId IS NULL
                    AND SprintId IS NOT NULL
                    ) THEN 'Sprint' ELSE Catagory END
        ) AS ProjectType) as CAResult

Answer 3

CTE可能是你最好的选择。

WITH CTE
AS
(
SELECT '3' AS RowType
  ,DTH.EnteredBy AS Person
  ,COALESCE(PDT.[Name], APP.AppName) AS Project
  ,(
    CASE WHEN (
                STY.KanBanProductId IS NOT NULL
                AND STY.SprintId IS NULL
                ) THEN 'Kanban' WHEN (
                STY.KanBanProductId IS NULL
                AND STY.SprintId IS NOT NULL
                ) THEN 'Sprint' ELSE SCY.Catagory END
    ) AS ProjectType
  FROM Table STY
)

select c.*, dbo.primaryTheme(STY.[Number], c.ProjectType) from CTE as c join Table STY on t.ID = c.id

将前一列的逻辑作为参数传递

3 个答案: