JSON_EXTRACT_PATH_TEXT

通过 path_name 从 JSON 字符串中提取值。 如果任一参数为 NULL，则返回 NULL，否则返回一个字符串（String）类型的值。 此函数等价于 to_varchar(GET_PATH(PARSE_JSON(JSON), PATH_NAME))。

语法

JSON_EXTRACT_PATH_TEXT( <expr>, <path_name> )

参数

参数	描述
<expr>	JSON 字符串值。
<path_name>	由字段名称串联而成的字符串值。

返回类型

字符串（String）

示例

SELECT json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k1[0]');
+-------------------------------------------------------------------------+
| json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k1[0]') |
+-------------------------------------------------------------------------+
| 0                                                                       |
+-------------------------------------------------------------------------+

SELECT json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2:k3');
+-------------------------------------------------------------------------+
| json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2:k3') |
+-------------------------------------------------------------------------+
| 3                                                                       |
+-------------------------------------------------------------------------+

SELECT json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2.k4');
+-------------------------------------------------------------------------+
| json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2.k4') |
+-------------------------------------------------------------------------+
| 4                                                                       |
+-------------------------------------------------------------------------+

SELECT json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2.k5');
+-------------------------------------------------------------------------+
| json_extract_path_text('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}', 'k2.k5') |
+-------------------------------------------------------------------------+
| NULL                                                                    |
+-------------------------------------------------------------------------+