SQL 服务器 - 选择如何在树的顶层传播值时？ （包括SQLFiddle）

Question

我需要在树的顶层传播值：

CREATE TABLE [dbo].[area](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [name] [varchar](50) NOT NULL,
    [parent_id] [int] NULL,
    [color] [varchar](50) NULL,
    [priority] [int] NULL)

insert into area values('root', NULL, NULL, NULL);
insert into area values('test1', 1, NULL, NULL);
insert into area values('test2', 2, 'red', 50);
insert into area values('test3', 5, 'blue', 1);
insert into area values('test4', 1, 'yellow', 10);

id	parent_id	name	color	priority	level	path_id	path_name
1	(null)	root	(null)	(null)	0	1	root
2	1	test1	(null)	(null)	1	1	root\test1
5	1	test4	yellow	10	1	1	root\test4
4	5	test3	blue	1	2	1	root\test4\test3
3	2	test2	red	50	2	1	root\test1\test2

我正在使用以下查询执行此操作（下一个过程使用 CTE）：

WITH tPATH
AS (SELECT id,
           parent_id,
           name,
           color,
           priority,
           0 as [level],
           CAST(id AS NVARCHAR(MAX)) As path_id,
           CAST(name AS NVARCHAR(MAX)) As path_name
    FROM area
    WHERE parent_id is NULL
    UNION ALL
    SELECT area.id,
           area.parent_id,
           area.name,
           area.color,
           area.priority,
           [level] + 1,
           CONCAT(tPATH.path_id, '\', CAST(area.id AS NVARCHAR(MAX))),
           CONCAT(tPATH.path_name, '\', CAST(area.name AS NVARCHAR(MAX)))
    FROM area
        INNER JOIN tPATH
            ON area.parent_id = tPATH.id
   )
select *
from tPATH;

优先级 1 最好。所以我想要这个：

• blue 必须在 id 1 中，优先级为 1，
• red 必须在 id 2 中，优先级为 50，
• blue 必须在 id 5 中，优先级为 1，
• id 4和3保持不变

id	parent_id	name	color	priority	level	path_id	path_name
1	(null)	root	blue	1	0	1	root
2	1	test1	red	50	1	1	root\test1
5	1	test4	blue	1	1	1	root\test4
4	5	test3	blue	1	2	1	root\test4\test3
3	2	test2	red	50	2	1	root\test1\test2

有什么想法吗（在顶层传播颜色和优先级）？ The fiddle || SQLize

提前致谢。

Answer 1

您可以使用查询

计算一个有效优先级作为所有节点后代的最小值

WITH tPATH
AS (SELECT id, 
           id [top],
           parent_id,
           priority
    FROM area

    UNION ALL
    
    SELECT area.id, 
           [top],
           area.parent_id,
           area.priority
    FROM area
    INNER JOIN tPATH
            ON area.parent_id = tPATH.id
   )
select [top] as id, min(priority) effective_priority
from tPATH
group by [top];

Answer 2

根据@Serg 的回答，我创建了这段代码，它给了我预期的结果。能再简单点吗？

WITH tPATH
AS (SELECT id,
           parent_id,
           name,
           color,
           priority,
           0 [level],
           CAST(id AS NVARCHAR(MAX)) [path_id],
           CAST(name AS NVARCHAR(MAX)) [path_name]
    FROM area
    WHERE parent_id is NULL
    UNION ALL
    SELECT area.id,
           area.parent_id,
           area.name,
           area.color,
           area.priority,
           [level] + 1,
           CONCAT(tPATH.path_id, '\', CAST(area.id AS NVARCHAR(MAX))),
           CONCAT(tPATH.path_name, '\', CAST(area.name AS NVARCHAR(MAX)))
    FROM area
        INNER JOIN tPATH
            ON area.parent_id = tPATH.id
   ),
     tDIFF
AS (SELECT id,
           id [top],
           parent_id,
           priority
    FROM area
    UNION ALL
    SELECT area.id,
           [top],
           area.parent_id,
           area.priority
    FROM area
        INNER JOIN tDIFF
            ON area.parent_id = tDIFF.id
   ),
     tDIFFEND
AS (select [top] as id,
           min(priority) effective_priority
    from tDIFF
    group by [top]
   )
SELECT tPATH.id,
       tPATH.parent_id,
       tPATH.name,
       area.color,
       effective_priority [priority],
       tPATH.level,
       tPATH.path_id,
       tPATH.path_name
from tPATH
    INNER JOIN tDIFFEND
        ON tDIFFEND.id = tPATH.id
    LEFT JOIN area
        ON area.priority = effective_priority;