SQL：如何从递归查询创建视图？

Posted 2023-03-16

【中文标题】SQL：如何从递归查询创建视图？

【英文标题】：SQL: How to create view from a recursive query?

【发布时间】：2011-04-25 23:17:38

【问题描述】：

问题：我想从递归查询中得出一个视图。

查询与此处的查询具有相同的结构： http://forums.asp.net/t/1207101.aspx

并将树视图表示为有序数据集。

如何创建执行此操作的视图：

;WITH Tree (ID, [NAME], PARENT_ID, Depth, Sort) AS
(
    SELECT ID, [NAME], PARENT_ID, 0 AS Depth, CONVERT(varchar(255), [Name]) AS Sort FROM Category
    WHERE PARENT_ID = 0
    UNION ALL
    SELECT CT.ID, CT.[NAME], CT.PARENT_ID, Parent.Depth + 1 AS Depth, 
    CONVERT(varchar(255), Parent.Sort + ' | ' + CT.[NAME]) AS Sort
    FROM Category CT
    INNER JOIN Tree as Parent ON Parent.ID = CT.PARENT_ID
)

-- HERE IS YOUR TREE, Depths gives you the level starting with 0 and Sort is the Name based path
SELECT ID, [NAME], PARENT_ID, Depth, Sort FROM Tree
ORDER BY Sort

【问题讨论】：

您最好创建一个执行此操作的内联表值函数。然后你可以参数化你传递给它的 Parent_Id。

最好在视图中进行，并且可能将主根 uid 添加为列，并从存储过程中查询该视图。当你有很多数据时，表值函数会变得很慢，因为它们会在内存中创建临时表，如果内存不足，它们会被交换。

【参考方案1】：

应该很简单：

CREATE VIEW YourViewName
AS
    WITH Tree (ID, [NAME], PARENT_ID, Depth, Sort) AS
    (
        SELECT ID, [NAME], PARENT_ID, 0 AS Depth, CONVERT(varchar(255), [Name]) AS Sort         
        FROM Category
        WHERE PARENT_ID = 0
        UNION ALL
        SELECT CT.ID, CT.[NAME], CT.PARENT_ID, Parent.Depth + 1 AS Depth, 
        CONVERT(varchar(255), Parent.Sort + ' | ' + CT.[NAME]) AS Sort
        FROM Category CT
        INNER JOIN Tree as Parent ON Parent.ID = CT.PARENT_ID
    )

    -- HERE IS YOUR TREE, Depths gives you the level starting with 0 and Sort is the Name based path
    SELECT ID, [NAME], PARENT_ID, Depth, Sort FROM Tree
GO

【讨论】：

啊，分号，抱歉没看到。 PS：不，不是那么简单，只是几乎：您需要删除 order by 或将前 100% 添加到 select 语句中；-)

您需要删除 ORDER BY - 它不属于视图，SQL 无论如何都会拒绝它

@Quandary, @Damien：感谢ORDER BY 的关注。剪切-粘贴编码的危害之一！ :-) 我会适当更新。