执行显示所有数据的分层查询答案

【问题标题】：Executing Hierarchical Query showing all data执行显示所有数据的分层查询
【发布时间】：2014-12-16 07:12:25
【问题描述】：

我正在尝试 Hierarchical select 在 oracle 中查询，但无法从那里得到想要的结果，并且不明白我是在写错误的查询还是我的表中有错误的数据？就像

I_ID    NAME    MGR_ID  LEVEL   PATH
1       SMITH       0    0      /SMITH
2       ALLEN       1    1      /SMITH/ALLEN
3       WARD        1    1      /SMITH/WARD
5       MARTIN      1    1      /SMITH/MARTIN
4       JONES       2    2      /SMITH/ALLEN/JONES
7       CLARK       2    2      /SMITH/ALLEN/CLARK
6       BLAKE       3    2      /SMITH/WARD/BLAKE
8       SCOTT       7    3      /SMITH/ALLEN/CLARK/SCOTT
9       KING        7    3      /SMITH/ALLEN/CLARK/KING
10      TURNER      8    4      /SMITH/ALLEN/CLARK/SCOTT/TURNER
12      JAMES       8    4      /SMITH/ALLEN/CLARK/SCOTT/JAMES
11      ADAMS       10   5      /SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS
13      FORD        11   6      /SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS/FORD
14      MILLER      13   7      /SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS/FORD/MILLER

请帮我参考check

【问题讨论】：

标签： sql oracle11g hierarchy

【解决方案1】：

我使用了与您类似的查询，并将结果分组以只为每个 i_id 选择具有最大级别的一行。

查询：

select *
from (
    select
        i_id, name, mgr_id, max(plevel) - 1 "level",
        max(path) keep (dense_rank last order by plevel) path
from (
        select i_id, name, mgr_id, level plevel, SYS_CONNECT_BY_PATH(name, '/') path
        from emp
        connect by prior i_id = mgr_id
    )
group by i_id, name, mgr_id
)
order by "level", i_id

Results：

| I_ID |   NAME | MGR_ID | LEVEL |PATH                                              |
|------|--------|--------|-------|--------------------------------------------------|
|    1 |  SMITH |      0 |     0 |/SMITH                                            |
|    2 |  ALLEN |      1 |     1 |/SMITH/ALLEN                                      |
|    3 |   WARD |      1 |     1 |/SMITH/WARD                                       |
|    5 | MARTIN |      1 |     1 |/SMITH/MARTIN                                     |
|    4 |  JONES |      2 |     2 |/SMITH/ALLEN/JONES                                |
|    6 |  BLAKE |      3 |     2 |/SMITH/WARD/BLAKE                                 |
|    7 |  CLARK |      2 |     2 |/SMITH/ALLEN/CLARK                                |
|    8 |  SCOTT |      7 |     3 |/SMITH/ALLEN/CLARK/SCOTT                          |
|    9 |   KING |      7 |     3 |/SMITH/ALLEN/CLARK/KING                           |
|   10 | TURNER |      8 |     4 |/SMITH/ALLEN/CLARK/SCOTT/TURNER                   |
|   12 |  JAMES |      8 |     4 |/SMITH/ALLEN/CLARK/SCOTT/JAMES                    |
|   11 |  ADAMS |     10 |     5 |/SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS             |
|   13 |   FORD |     11 |     6 |/SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS/FORD        |
|   14 | MILLER |     13 |     7 |/SMITH/ALLEN/CLARK/SCOTT/TURNER/ADAMS/FORD/MILLER |

【讨论】：