使用 CTE 的相邻列表和递归查询，如何回填？

Question

我有一个查询，它从父子表（自联接、相邻列表）生成扁平层次结构。问题是此查询为没有任何子级的级别生成 NULL。现在我的意图是“回填”这些级别以生成一个在级别列中不包含任何 NULL 值的表。我应该如何修改这个查询？

示例数据：

SET NOCOUNT ON;
USE Tempdb;

IF OBJECT_ID('dbo.Employees', 'U') IS NOT NULL DROP TABLE dbo.Employees;

CREATE TABLE dbo.Employees
(
  empid   INT         NOT NULL PRIMARY KEY,
  mgrid   INT         NULL     REFERENCES dbo.Employees,
  empname VARCHAR(25) NOT NULL,
  salary  MONEY       NOT NULL,
  CHECK (empid <> mgrid),
  CHECK (empid > 0)
);

CREATE UNIQUE INDEX idx_unc_mgrid_empid ON dbo.Employees(mgrid, empid);

INSERT INTO dbo.Employees(empid, mgrid, empname, salary) VALUES
  (1,  NULL, 'David'  , $10000.00),
  (2,  1,    'Eitan'  ,  $7000.00),
  (3,  1,    'Ina'    ,  $7500.00),
  (4,  2,    'Seraph' ,  $5000.00),
  (5,  2,    'Jiru'   ,  $5500.00),
  (6,  2,    'Steve'  ,  $4500.00),
  (7,  3,    'Aaron'  ,  $5000.00),
  (8,  5,    'Lilach' ,  $3500.00),
  (9,  7,    'Rita'   ,  $3000.00),
  (10, 5,    'Sean'   ,  $3000.00),
  (11, 7,    'Gabriel',  $3000.00),
  (12, 9,    'Emilia' ,  $2000.00),
  (13, 9,    'Michael',  $2000.00),
  (14, 9,    'Didi'   ,  $1500.00);

@Andomar提供的查询

; with  Tree as
        (
        SELECT  empid
        ,       mgrid
        ,       1 as lv
        ,       1 as level1
        ,       null as level2
        ,       null as level3
        ,       null as level4
        ,       null as level5
        FROM    Employees
        WHERE   mgrid IS NULL 
        UNION ALL
        SELECT  E.empid
        ,       E.mgrid
        ,       T.lv + 1
        ,       T.level1
        ,       case when T.lv = 1 then E.empid else t.level2 end
        ,       case when T.lv = 2 then E.empid else t.level3 end
        ,       case when T.lv = 3 then E.empid else t.level4 end
        ,       case when T.lv = 4 then E.empid else t.level5 end
        FROM    Employees AS E
        JOIN    Tree T
        ON      E.mgrid = T.empid
        )
select  *
from    Tree
order by empid

这会产生

+-------+--------+----+--------+--------+--------+--------+--------+
| EMPID | MGRID  | LV | LEVEL1 | LEVEL2 | LEVEL3 | LEVEL4 | LEVEL5 |
+-------+--------+----+--------+--------+--------+--------+--------+
|     1 | (null) |  1 |      1 | (null) | (null) | (null) | (null) |
|     2 | 1      |  2 |      1 | 2      | (null) | (null) | (null) |
|     3 | 1      |  2 |      1 | 3      | (null) | (null) | (null) |
|     4 | 2      |  3 |      1 | 2      | 4      | (null) | (null) |
|     5 | 2      |  3 |      1 | 2      | 5      | (null) | (null) |
|     6 | 2      |  3 |      1 | 2      | 6      | (null) | (null) |
|     7 | 3      |  3 |      1 | 3      | 7      | (null) | (null) |
|     8 | 5      |  4 |      1 | 2      | 5      | 8      | (null) |
|     9 | 7      |  4 |      1 | 3      | 7      | 9      | (null) |
|    10 | 5      |  4 |      1 | 2      | 5      | 10     | (null) |
|    11 | 7      |  4 |      1 | 3      | 7      | 11     | (null) |
|    12 | 9      |  5 |      1 | 3      | 7      | 9      | 12     |
|    13 | 9      |  5 |      1 | 3      | 7      | 9      | 13     |
|    14 | 9      |  5 |      1 | 3      | 7      | 9      | 14     |
+-------+--------+----+--------+--------+--------+--------+--------+

但我们的想法是实现这一目标

+-------+--------+----+--------+--------+--------+--------+--------+
| EMPID | MGRID  | LV | LEVEL1 | LEVEL2 | LEVEL3 | LEVEL4 | LEVEL5 |
+-------+--------+----+--------+--------+--------+--------+--------+
|     1 | (null) |  1 |      1 | 1      | 1      | 1      | 1      |
|     2 | 1      |  2 |      1 | 2      | 2      | 2      | 2      |
|     3 | 1      |  2 |      1 | 3      | 3      | 3      | 3      |
|     4 | 2      |  3 |      1 | 2      | 4      | 4      | 4      |
|     5 | 2      |  3 |      1 | 2      | 5      | 5      | 5      |
|     6 | 2      |  3 |      1 | 2      | 6      | 6      | 6      |
|     7 | 3      |  3 |      1 | 3      | 7      | 7      | 7      |
|     8 | 5      |  4 |      1 | 2      | 5      | 8      | 8      |
|     9 | 7      |  4 |      1 | 3      | 7      | 9      | 9      |
|    10 | 5      |  4 |      1 | 2      | 5      | 10     | 10     |
|    11 | 7      |  4 |      1 | 3      | 7      | 11     | 11     |
|    12 | 9      |  5 |      1 | 3      | 7      | 9      | 12     |
|    13 | 9      |  5 |      1 | 3      | 7      | 9      | 13     |
|    14 | 9      |  5 |      1 | 3      | 7      | 9      | 14     |
+-------+--------+----+--------+--------+--------+--------+--------+

Answer 1

只需在最后一次选择中使用coalesce() 即可按照您想要的方式修改结果。

see sql-fiddle here

Answer 2

只需在树 CTE 之后添加以下内容

Select empid,mgrid,lv,
        level1 = coalesce(level1,Rn),
        level2 = coalesce(level2,Rn),
        level3 = coalesce(level3,Rn),
        level4 = coalesce(level4,Rn),
        level5 = coalesce(level5,Rn)
from
(select  empid,mgrid,lv,level1,level2,level3,level4,level5,Row_Number()Over(Order By empid) as Rn
from    Tree)x

Answer 3

我发现这也有效：

; with  Tree as
        (
        SELECT  empid
        ,       mgrid
        ,       1 as lv
        ,       1 as level1
        ,       null as level2
        ,       null as level3
        ,       null as level4
        ,       null as level5
        FROM    Employees
        WHERE   mgrid IS NULL 
        UNION ALL
        SELECT  E.empid
        ,       E.mgrid
        ,       T.lv + 1
        ,       T.level1
        ,       case when T.lv = 1 then E.empid else t.level2 end
        ,       case when T.lv = 2 then E.empid else t.level3 end
        ,       case when T.lv = 3 then E.empid else t.level4 end
        ,       case when T.lv = 4 then E.empid else t.level5 end
        FROM    Employees AS E
        JOIN    Tree T
        ON      E.mgrid = T.empid
        )
select  empid, 
        mgrid, 
        lv, 
        level1,
        level2 = coalesce(level2, level1),
        level3 = coalesce(level3, level2, level1),
        level4 = coalesce(level4, level3, level2, level1),
        level5 = coalesce(level5, level4, level3, level2, level1)
from Tree
order by empid