從MySQL JSON列中將JSON對象的值提取為數組

Question

我有一個json類型的MySQL列。 在那里，存儲了像JSON對象這樣的字典。 現在，我想從這個JSON對象中提取值並創建一個JSON數組。

我怎樣才能做到這一點？

示例查詢

with json_objs(json_col) as (
  select CAST('{"key1": "value1", "key2": "value2"}' AS JSON)
  UNION ALL
  select CAST('{"key3": "value3", "key4": "value4"}' AS JSON)
)
select SOME_EXPR_I_CAN_T_FIGURE_OUT from json_objs

預期結果

+----------------------+
| resulting_column     |
+----------------------+
| ["value1", "value2"] |
| ["value3", "value4"] |
+----------------------+

（如果需要表DDL :)

CREATE TABLE `json_objs` (
  `json_col` json DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8

Answer 1

您可以在表達式column -> path使用->運算符，如下所示：

create table table1 (
   json_dict JSON
);

insert into table1 values('{"ak":"av","bk":"bv"}');
insert into table1 values('{"ak2":"av2","bk2":"bv2"}');

select * from table1;
+------------------------------+
| json_dict                    |
+------------------------------+
| {"ak": "av", "bk": "bv"}     |
| {"ak2": "av2", "bk2": "bv2"} |
+------------------------------+
2 rows in set (0.00 sec)

select json_dict->"$.*" from table1;
+------------------+
| json_dict->"$.*" |
+------------------+
| ["av", "bv"]     |
| ["av2", "bv2"]   |
+------------------+
2 rows in set (0.00 sec)

https://dev.mysql.com/doc/refman/8.0/en/json-search-functions.html#operator_json-column-path

Answer 2

除了->運算符，您還可以使用Json_Extract()函數：

架構（MySQL v8.0）

create table table1 (
   json_dict JSON
);

insert into table1 values('{"ak":"av","bk":"bv"}');
insert into table1 values('{"ak2":"av2","bk2":"bv2"}');

---

查詢＃1

select JSON_EXTRACT(json_dict, '$.*') from table1;

| JSON_EXTRACT(json_dict, '$.*') |
| ------------------------------ |
| ["av", "bv"]                   |
| ["av2", "bv2"]                 |

---

查看DB小提琴