MySQL5.7 JSON类型及其相关函数的学习

mysql> CREATE TABLE `json_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `info` json NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

mysql> select * from json_table ;
+----+------------------------------+
| id | info                         |
+----+------------------------------+
|  1 | {"age": 24, "name": "lucy"}  |
|  2 | {"age": 20, "name": "lili"}  |
|  3 | {"age": 25, "name": "curry"} |
+----+------------------------------+
3 rows in set (0.00 sec)

JSON查询

提取json字段：json列->'$.键' 或 JSON_EXTRACT(json列 , '$.键')
去掉json字段双引号：JSON_UNQOUTE() 或者 json列->>'$.键'

提取JSON 字段的表达式可以用于SELECT查询列表，WHERE/HAVING , ORDER/GROUP BY语句中，JSON 中的元素搜索也是严格区分变量类型

json不同于字符串，不能当作字符串直接做比较，通过CAST()将字符串转换成JSON形式，再进行比较，后面举栗

举个栗子：

json列->'$.键' 查询：

mysql> select id, info->'$.name' as name from json_table ;
+----+---------+
| id | name    |
+----+---------+
|  1 | "lucy"  |
|  2 | "lili"  |
|  3 | "curry" |
+----+---------+
3 rows in set (0.00 sec)

mysql> select id, info->'$.name' as name from json_table where info->'$.age' >=24;
+----+---------+
| id | name    |
+----+---------+
|  1 | "lucy"  |
|  3 | "curry" |
+----+---------+
2 rows in set (0.00 sec)

JSON_EXTRACT(json列 , '$.键')查询：

mysql> select id, json_extract(info, '$.name') as name from json_table ;
+----+---------+
| id | name    |
+----+---------+
|  1 | "lucy"  |
|  2 | "lili"  |
|  3 | "curry" |
+----+---------+
3 rows in set (0.05 sec)

mysql> select id, json_extract(info, '$.name') as name from json_table where json_extract(info, '$.age') >= 24; 
+----+---------+
| id | name    |
+----+---------+
|  1 | "lucy"  |
|  3 | "curry" |
+----+---------+
2 rows in set (0.00 sec)

JSON_UNQOUTE()方法举栗：

mysql> select id, json_unquote(json_extract(info, '$.name')) as name from json_table ;
+----+-------+
| id | name  |
+----+-------+
|  1 | lucy  |
|  2 | lili  |
|  3 | curry |
+----+-------+
3 rows in set (0.00 sec)

mysql> select id, info->>'$.name' as name from json_table ;
+----+-------+
| id | name  |
+----+-------+
|  1 | lucy  |
|  2 | lili  |
|  3 | curry |
+----+-------+
3 rows in set (0.00 sec)

JSON字段与字符串比较举栗：

mysql> select * from json_table where info = '{"age": 25, "name": "curry"}';
Empty set (0.00 sec)

mysql> select * from json_table where info = cast('{"age": 25, "name": "curry"}' as JSON);
+----+------------------------------+
| id | info                         |
+----+------------------------------+
|  3 | {"age": 25, "name": "curry"} |
+----+------------------------------+
1 row in set (0.00 sec)

虚拟列

值得一提的是，可以通过虚拟列对JSON类型的指定属性进行快速查询，

栗如，创建索引：

mysql> alter table json_table add name varchar(20) generated always as (info->'$.name') virtual ;
Query OK, 0 rows affected (0.35 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from json_table ;
+----+------------------------------+---------+
| id | info                         | name    |
+----+------------------------------+---------+
|  1 | {"age": 24, "name": "lucy"}  | "lucy"  |
|  2 | {"age": 20, "name": "lili"}  | "lili"  |
|  3 | {"age": 25, "name": "curry"} | "curry" |
|  4 | {"age": 24, "name": "tom"}   | "tom"   |
|  5 | {"age": 24, "name": "jurry"} | "jurry" |
|  6 | {"age": 30, "name": "tmry"}  | "tmry"  |
+----+------------------------------+---------+
6 rows in set (0.00 sec)

mysql> select * from json_table where name=""tom"";
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tom""' at line 1
mysql> select * from json_table where name="\"tom\"";
+----+----------------------------+-------+
| id | info                       | name  |
+----+----------------------------+-------+
|  4 | {"age": 24, "name": "tom"} | "tom" |
+----+----------------------------+-------+
1 row in set (0.00 sec)
mysql> alter table json_table add index name_idx(name) ;
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table json_table \G
*************************** 1. row ***************************
       Table: json_table
Create Table: CREATE TABLE `json_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `info` json NOT NULL,
  `name` varchar(20) GENERATED ALWAYS AS (json_extract(`info`,'$.name')) VIRTUAL,
  PRIMARY KEY (`id`),
  KEY `name_idx` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

mysql> alter table json_table rename index name_idx to idx_name ;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table json_table \G                           
*************************** 1. row ***************************
       Table: json_table
Create Table: CREATE TABLE `json_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `info` json NOT NULL,
  `name` varchar(20) GENERATED ALWAYS AS (json_extract(`info`,'$.name')) VIRTUAL,
  PRIMARY KEY (`id`),
  KEY `idx_name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

MySQL5.7 JSON类型及其相关函数的学习

JSON查询

虚拟列

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