GET_PATH
从 VARIANT 中通过 path_name 提取值。
如果任一参数为 NULL，则返回值为 Variant 或 NULL。
GET_PATH 等同于一系列 GET 函数的链式调用，path_name 由一系列以句点 (.)、冒号 (:) 或索引运算符 ([index]) 开头 的字段名连接而成。第一个字段名不需要指定前导标识符。
语法
GET_PATH( <variant>, <path_name> )
参数
| 参数 | 描述 |
|---|---|
<variant> | 包含 ARRAY 或 OBJECT 的 VARIANT 值 |
<path_name> | 由一系列字段名连接而成的字符串值 |
返回类型
VARIANT
示例
SELECT get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k1[0]');
+-----------------------------------------------------------------------+
| get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k1[0]') |
+-----------------------------------------------------------------------+
| 0 |
+-----------------------------------------------------------------------+
SELECT get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2:k3');
+-----------------------------------------------------------------------+
| get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2:k3') |
+-----------------------------------------------------------------------+
| 3 |
+-----------------------------------------------------------------------+
SELECT get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2.k4');
+-----------------------------------------------------------------------+
| get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2.k4') |
+-----------------------------------------------------------------------+
| 4 |
+-----------------------------------------------------------------------+
SELECT get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2.k5');
+-----------------------------------------------------------------------+
| get_path(parse_json('{"k1":[0,1,2], "k2":{"k3":3,"k4":4}}'), 'k2.k5') |
+-----------------------------------------------------------------------+
| NULL |
+-----------------------------------------------------------------------+
