Question

我无法弄清楚如何使用递归CTE递归地命令我的结果。这就是我的意思（这是一个简化的数据集）：

我将此作为输入：

declare @sections table (id int, parent int);

insert into @sections values (1, 1);
insert into @sections values (2, 2);
insert into @sections values (3, 2);
insert into @sections values (4, 2);
insert into @sections values (5, 4);
insert into @sections values (6, 1);
insert into @sections values (7, 6);
insert into @sections values (8, 6);
insert into @sections values (9, 6);
insert into @sections values (10, 9);

-- hierarchical view
--1
--  6
--      7
--      8
--          10
--      9
--2
--  3
--  4
--      5

我希望这是输出 编辑：行的顺序是这里的重要部分

--  id  parent  depth
--  1   1       0
--  6   1       1
--  7   6       2
--  8   6       2
-- 10   8       3
--  9   6       2
--  2   2       0

这是我能做的最好的事情：

with section_cte as
(
    select id, parent, 0 'depth' from @sections where id = parent
    union all
    select cte.id, cte.parent, depth + 1 
    from @sections s join section_cte cte on s.parent = cte.id where s.id <> s.parent
)
select *from section_cte

有人可以帮我调整一下这个查询以获得我需要的东西吗？

谢谢！

Answer 1

您错过了需要识别深度的部分来自cte

WITH CTE AS (
SELECT
    id
    , parent
    , 0 AS depth
FROM
    @sections
WHERE
    id=parent

UNION ALL

SELECT
    s.id
    , s.parent
    , c.depth + 1
FROM
    @sections s
    JOIN CTE c ON s.parent=c.id AND s.id <> s.parent
)
SELECT *
FROM CTE;

Answer 2

在递归构建期间，添加序列是一件小事。在下面的示例中，订单由标题的字母顺序驱动，但您可以使用任何其他可用的键/序列。

Declare @Table table (ID int,Pt int,Title varchar(50))
Insert into @Table values (0,null,'Tags'),(1,0,'Transportation'),(2,1,'Boats'),(3,1,'Cars'),(4,1,'Planes'),(5,1,'Trains'),(6,0,'Technology'),(7,6,'FTP'),(8,6,'HTTP'),(9,0,'Finance'),(10,9,'FTP'),(11,9,'401K'),(12,2,'Sail'),(13,2,'Powered'),(14,6,'Internet'),(15,6,'Database'),(16,15,'SQL Server'),(17,15,'MySQL'),(18,15,'MS Access')

Declare @Top  int = null          --<<  Sets top of Hier Try 9
Declare @Nest varchar(25) ='   '  --<<  Optional: Added for readability

;with cteHB (Seq,ID,Pt,Lvl,Title) as (
    Select  Seq  = cast(1000+Row_Number() over (Order by Title) as varchar(500))
           ,ID
           ,Pt
           ,Lvl=1
           ,Title 
     From   @Table 
     Where  IsNull(@Top,-1) = case when @Top is null then isnull(Pt,-1) else ID end
     Union  All
     Select Seq  = cast(concat(cteHB.Seq,'.',1000+Row_Number() over (Order by cteCD.Title)) as varchar(500))
           ,cteCD.ID
           ,cteCD.Pt,cteHB.Lvl+1
           ,cteCD.Title 
     From   @Table cteCD 
     Join   cteHB on cteCD.Pt = cteHB.ID)
     ,cteR1 as (Select Seq,ID,R1=Row_Number() over (Order By Seq) From cteHB)
     ,cteR2 as (Select A.Seq,A.ID,R2=Max(B.R1) From cteR1 A Join cteR1 B on (B.Seq like A.Seq+'%') Group By A.Seq,A.ID )
Select Hier='HierName'
      ,B.R1  
      ,C.R2
      ,A.ID
      ,A.Pt
      ,A.Lvl
      ,Title = Replicate(@Nest,A.Lvl) + A.Title
      --,A.Seq               --<< Normally Excluded, but you can see how the sequence is built
 From cteHB A
 Join cteR1 B on A.ID=B.ID
 Join cteR2 C on A.ID=C.ID
 Order By A.Seq              --<< Use R1 if Range Keys are used

返回

Hier        R1  R2  ID  Pt      Lvl    Title
HierName    1   19  0   NULL    1      Tags
HierName    2   4   9   0       2         Finance
HierName    3   3   11  9       3            401K
HierName    4   4   10  9       3            FTP
HierName    5   12  6   0       2         Technology
HierName    6   9   15  6       3            Database
HierName    7   7   18  15      4               MS Access
HierName    8   8   17  15      4               MySQL
HierName    9   9   16  15      4               SQL Server
HierName    10  10  7   6       3            FTP
HierName    11  11  8   6       3            HTTP
HierName    12  12  14  6       3            Internet
HierName    13  19  1   0       2         Transportation
HierName    14  16  2   1       3            Boats
HierName    15  15  13  2       4               Powered
HierName    16  16  12  2       4               Sail
HierName    17  17  3   1       3            Cars
HierName    18  18  4   1       3            Planes
HierName    19  19  5   1       3            Trains

现在，您可能已经注意到R1和R2。这些是我的范围键，通常用于聚合数据而不进行递归。如果您不需要或不需要这些，只需删除cteR1和cteR2（以及最终SELECT中的相应引用）。

修改

您还可以选择层次结构的一部分（即技术及其子项）。

Answer 3

您需要的技巧是创建一个符合您的业务规则的sortstring。这样的事情。

WITH CTE AS (
SELECT
    id, parent, 0 AS depth
    --For MS SQL Server 2012+
    ,cast(format(id,'0000') as varchar(max)) sort
    --For previous versions
    ,cast(stuff('0000',5-len(cast(id as varchar)),len(cast(id as varchar)),id) as varchar(max)) sort1
FROM @sections
WHERE id=parent
UNION ALL
SELECT s.id, s.parent, c.depth + 1
    ,sort + cast(format(s.id,'0000') as varchar(max)) sort
    ,sort + cast(stuff('0000',5-len(cast(s.id as varchar)),len(cast(s.id as varchar)),s.id) as varchar(max)) sort1
FROM @sections s
    inner join CTE c ON s.parent=c.id AND s.id <> s.parent
)
SELECT *
FROM CTE
order by sort --or by sort1 depending on version

TSQL递归CTE命令

3 个答案: