mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-13 19:14:30 +00:00
71 lines
1.9 KiB
Markdown
71 lines
1.9 KiB
Markdown
---
|
||
machine_translated: true
|
||
machine_translated_rev: 72537a2d527c63c07aa5d2361a8829f3895cf2bd
|
||
toc_priority: 45
|
||
toc_title: "\u5206\u5C42\u5B57\u5178"
|
||
---
|
||
|
||
# 分层字典 {#hierarchical-dictionaries}
|
||
|
||
ClickHouse支持分层字典与 [数字键](external-dicts-dict-structure.md#ext_dict-numeric-key).
|
||
|
||
看看下面的层次结构:
|
||
|
||
``` text
|
||
0 (Common parent)
|
||
│
|
||
├── 1 (Russia)
|
||
│ │
|
||
│ └── 2 (Moscow)
|
||
│ │
|
||
│ └── 3 (Center)
|
||
│
|
||
└── 4 (Great Britain)
|
||
│
|
||
└── 5 (London)
|
||
```
|
||
|
||
这种层次结构可以表示为下面的字典表。
|
||
|
||
| region_id | parent_region | region_name |
|
||
|------------|----------------|--------------|
|
||
| 1 | 0 | 俄罗斯 |
|
||
| 2 | 1 | 莫斯科 |
|
||
| 3 | 2 | 中心 |
|
||
| 4 | 0 | 英国 |
|
||
| 5 | 4 | 伦敦 |
|
||
|
||
此表包含一列 `parent_region` 包含该元素的最近父项的键。
|
||
|
||
ClickHouse支持 [等级](external-dicts-dict-structure.md#hierarchical-dict-attr) 属性为 [外部字典](index.md) 属性。 此属性允许您配置类似于上述的分层字典。
|
||
|
||
该 [独裁主义](../../../sql-reference/functions/ext-dict-functions.md#dictgethierarchy) 函数允许您获取元素的父链。
|
||
|
||
对于我们的例子，dictionary的结构可以是以下内容:
|
||
|
||
``` xml
|
||
<dictionary>
|
||
<structure>
|
||
<id>
|
||
<name>region_id</name>
|
||
</id>
|
||
|
||
<attribute>
|
||
<name>parent_region</name>
|
||
<type>UInt64</type>
|
||
<null_value>0</null_value>
|
||
<hierarchical>true</hierarchical>
|
||
</attribute>
|
||
|
||
<attribute>
|
||
<name>region_name</name>
|
||
<type>String</type>
|
||
<null_value></null_value>
|
||
</attribute>
|
||
|
||
</structure>
|
||
</dictionary>
|
||
```
|
||
|
||
[原始文章](https://clickhouse.tech/docs/en/query_language/dicts/external_dicts_dict_hierarchical/) <!--hide-->
|