Question

我有一个查询，它从父子表（自连接，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表，该表在级别列中不包含任何NULL值。我该如何修改此查询？

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     |
+-------+--------+----+--------+--------+--------+--------+--------+

但想法是实现这个目标

+-------+--------+----+--------+--------+--------+--------+--------+
| 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

只需一个简单的尝试就可以按照您希望的方式在最后一次选择中使用coalesce()修改结果。

see sql-fiddle here

Answer 2

在Tree 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

enter image description here

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

相邻列表和使用CTE的递归查询，如何回填？

3 个答案: