Question

create table #tbl
(
ID int,
[Object] varchar(1),
[Subject] varchar(1)
)

insert into #tbl
select 1, 'A', 'B' union all
select 2, 'A', 'C' union all
select 3, 'A', 'D' union all
select 4, 'B', 'E' union all
select 5, 'B', 'F' union all
select 6, 'D', 'G' union all
select 7, 'D', 'H' union all
select 8, 'G', 'I' union all
select 9, 'G', 'J' union all
select 10, 'I', 'K' union all
select 11, 'I', 'L'

select *
from #tbl

我有一个关联表，下面有数据。我需要创建一个查询，该查询为我提供以下数据集的结果。当我想要获取A包含的所有数据时，我需要使用一个原子值。原子值是叶子水平。我需要循环抛出数据集几次。 A是3倍，对于B仅是1，对于D是2倍。最好的查询技术是什么？我正在尝试通过Common Table Expression使用递归查询，但没有得到正确的结果。

 ID OBJECT SUBJECT
  1    A      B
  2    A      C
  3    A      D
  4    B      E
  5    B      F
  6    D      G
  7    D      H
  8    G      I
  9    G      J
  10   I      K
  11   I      L

A：B（E，F），C，D（G（I（K，L），J），H）> E，F，C，K，L，J，H
B：E，F
D：G（I（K，L），J），H> K，L，J，H
G：I（K，L），J> K，L，J
我：K，L

编辑

所需的表输出：

ID OBJECT SUBJECT
 1    A      E
 2    A      F
 3    A      C
 4    A      K
 5    А      L
 6    А      J
 7    А      H
 8    B      E
 9    B      F
 10   D      K
 11   D      L
 12   D      J
 13   D      H
 14   G      K
 15   G      L
 16   G      J
 17   I      K
 18   I      L

我尝试以下查询：

;with cte as 
(
select id, object, subject
from #tbl

union all

select a.id, a.object, a.subject
from #tbl a
join cte b on a.subject=b.object
)
select *
from cte

有人可以帮助我吗？

最好的问候

Answer 1

我认为我理解您的逻辑（实际上会产生与您期望的输出不同的结果，但我仍然认为这是不正确的），并且您需要的递归有点不寻常，因为它需要在末尾进行自我联接删除不是层次结构中最低级别的所有行：

declare @t table(ID int
                ,[Object] varchar(1)
                ,[Subject] varchar(1)
                );
insert into @t values(1,  'A', 'B'),(2,  'A', 'C'),(3,  'A', 'D'),(4,  'B', 'E'),(5,  'B', 'F'),(6,  'D', 'G'),(7,  'D', 'H'),(8,  'G', 'I'),(9,  'G', 'J'),(10, 'I', 'K'),(11, 'I', 'L');

with r as
(
    select ID
            ,[Object]
            ,[Subject]
            ,0 as Hierarchy
            ,row_number() over (order by ID) as rn
    from @t

    union all

    select t.ID
            ,r.[Object]
            ,t.[Subject]
            ,r.Hierarchy + 1
            ,r.rn
    from r
        join @t as t
            on r.[Subject] = t.[Object]
)
select row_number() over (order by r.[Object], r.rn, r.Hierarchy desc, r.[Subject]) as ID
        ,r.[Object]
        ,r.[Subject]
from r
    left join r r2
        on r.[Subject] = r2.[Object]
where r2.[Object] is null
order by ID;

输出：

+----+--------+---------+
| ID | Object | Subject |
+----+--------+---------+
|  1 | A      | E       |
|  2 | A      | F       |
|  3 | A      | C       |
|  4 | A      | K       |
|  5 | A      | L       |
|  6 | A      | J       |
|  7 | A      | H       |
|  8 | B      | E       |
|  9 | B      | F       |
| 10 | D      | K       |
| 11 | D      | L       |
| 12 | D      | J       |
| 13 | D      | H       |
| 14 | G      | K       |
| 15 | G      | L       |
| 16 | G      | J       |
| 17 | I      | K       |
| 18 | I      | L       |
+----+--------+---------+

Answer 2

使用recursive CTE的一种方法（如果不需要订购）

create table #tbl
(
ID int,
[Object] varchar(1),
[Subject] varchar(1)
)

insert into #tbl
select 1, 'A', 'B' union all
select 2, 'A', 'C' union all
select 3, 'A', 'D' union all
select 4, 'B', 'E' union all
select 5, 'B', 'F' union all
select 6, 'D', 'G' union all
select 7, 'D', 'H' union all
select 8, 'G', 'I' union all
select 9, 'G', 'J' union all
select 10, 'I', 'K' union all
select 11, 'I', 'L'

;With
rcte as
(
    -- Anchor member
    select  *, [object] as parent               
    from   #tbl

    union all

    -- Recursive member
    select  c.*, r.parent                 
    from    #tbl c
    inner join rcte r on c.Object = r.Subject
)
Select distinct parent, Subject from rcte x 
where subject not in (Select object from rcte y where x.parent = y.parent)

创建递归查询

2 个答案: