在邻接列表中查找子体深度

示例表

+-------------+----------------------+--------+
| category_id | name                 | parent |
+-------------+----------------------+--------+
|           1 | ELECTRONICS          |   NULL |
|           2 | TELEVISIONS          |      1 |
|           3 | TUBE                 |      2 |
|           4 | LCD                  |      2 |
|           5 | PLASMA               |      2 |
|           6 | PORTABLE ELECTRONICS |      1 |
|           7 | MP3 PLAYERS          |      6 |
|           8 | FLASH                |      7 |
|           9 | CD PLAYERS           |      6 |
|          10 | 2 WAY RADIOS         |      6 |
+-------------+----------------------+--------+

根据上面的示例表,我认为在Oracle中,我应该能够按照“SELECT。。。按“查找给定id的级别。例如,“MP3播放器”的级别为3。

借来的例子 Managing Hierarchical Data in MySQL

解决方案

SELECT MAX(level) "LEVEL"
FROM TEST_TABLE
START WITH category_id = 7 -- MP3 Players category_id
CONNECT BY category_id = PRIOR parent
ORDER BY LEVEL DESC