Oracle 在邻接列表表中查找子体深度

问题

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

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…CONNECT BY”来编写SQL，以查找给定id的级别。例如，“MP3播放器”的级别为3

借鉴

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

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您可以使用

level

pseudocolumn获取当前行的“深度”。考虑下面的陈述：

SELECT category_id, name, level,
 PRIOR name as parent_category
FROM test_table
START WITH parent is null
CONNECT BY PRIOR category_id = parent

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这是朝着正确的方向迈出的一步：更具体地说，我正在寻找能够为我提供特定id级别（例如7）的SQL。在我自己做了一些额外的搜索之后，我将我提出的解决方案添加到了最初的问题中。