---
{
    "title": "get_json_string",
    "language": "zh-CN"
}
---

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# get_json_string
## description
### Syntax

`VARCHAR get_json_string(VARCHAR json_str, VARCHAR json_path)


解析并获取 json 字符串内指定路径的字符串内容。
其中 json_path 必须以 $ 符号作为开头，使用 . 作为路径分割符。如果路径中包含 . ，则可以使用双引号包围。
使用 [ ] 表示数组下标，从 0 开始。
path 的内容不能包含 ", [ 和 ]。
如果 json_string 格式不对，或 json_path 格式不对，或无法找到匹配项，则返回 NULL。

## example

1. 获取 key 为 "k1" 的 value

```
mysql> SELECT get_json_string('{"k1":"v1", "k2":"v2"}', "$.k1");
+---------------------------------------------------+
| get_json_string('{"k1":"v1", "k2":"v2"}', '$.k1') |
+---------------------------------------------------+
| v1                                                |
+---------------------------------------------------+
```

2. 获取 key 为 "my.key" 的数组中第二个元素

```
mysql> SELECT get_json_string('{"k1":"v1", "my.key":["e1", "e2", "e3"]}', '$."my.key"[1]');
+------------------------------------------------------------------------------+
| get_json_string('{"k1":"v1", "my.key":["e1", "e2", "e3"]}', '$."my.key"[1]') |
+------------------------------------------------------------------------------+
| e2                                                                           |
+------------------------------------------------------------------------------+
```

3. 获取二级路径为 k1.key -> k2 的数组中，第一个元素
```
mysql> SELECT get_json_string('{"k1.key":{"k2":["v1", "v2"]}}', '$."k1.key".k2[0]');
+-----------------------------------------------------------------------+
| get_json_string('{"k1.key":{"k2":["v1", "v2"]}}', '$."k1.key".k2[0]') |
+-----------------------------------------------------------------------+
| v1                                                                    |
+-----------------------------------------------------------------------+
```

4. 获取数组中，key 为 "k1" 的所有 value
```
mysql> SELECT get_json_string('[{"k1":"v1"}, {"k2":"v2"}, {"k1":"v3"}, {"k1":"v4"}]', '$.k1');
+---------------------------------------------------------------------------------+
| get_json_string('[{"k1":"v1"}, {"k2":"v2"}, {"k1":"v3"}, {"k1":"v4"}]', '$.k1') |
+---------------------------------------------------------------------------------+
| ["v1","v3","v4"]                                                                |
+---------------------------------------------------------------------------------+
```
## keyword
GET_JSON_STRING,GET,JSON,STRING