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)
Creating JSON Values
MySQL里的json分为json array和json object。
-
JSON_TYPE()：查看字段类型
-
JSON_ARRAY()：返回json数组
-
JSON_OBJECT()：返回json对象
-
JSON_MERGE()：合并多个json文档
举个栗子：
#查看类型
mysql> select id, json_extract(info, '$.name') as name , json_type(json_extract(info, '$.name')) as type from json_table where id=3 ;
+----+---------+--------+
| id | name | type |
+----+---------+--------+
| 3 | "curry" | STRING |
+----+---------+--------+
1 row in set (0.00 sec)
#生成一个json数据组
mysql> select json_array('aaa', 'bbb', 'ddd') as array;
+-----------------------+
| array |
+-----------------------+
| ["aaa", "bbb", "ddd"] |
+-----------------------+
1 row in set (0.00 sec)
#生成一个json对象
mysql> select json_object('aaa', 1, 'bbb', 2, 'ddd', 3) as array;
+--------------------------------+
| array |
+--------------------------------+
| {"aaa": 1, "bbb": 2, "ddd": 3} |
+--------------------------------+
1 row in set (0.00 sec)
#将多个json文档合并
mysql> select json_merge(json_array('aaa', 'bbb', 'ddd'), json_object('aaa', 1, 'bbb', 2, 'ddd', 3)) as json ;
+-------------------------------------------------------+
| json |
+-------------------------------------------------------+
| ["aaa", "bbb", "ddd", {"aaa": 1, "bbb": 2, "ddd": 3}] |
+-------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)
JSON查询
MySQL里的json分为json array和json object
对于json array，在索引数据时用从0开始的下标进行索引，$表示整个json对象，例如：$[0]、$[1]
对于json object，在索引数据时用key进行索引，含有特殊字符的key要用""括起来，比如$."my name")
-
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->'$.age' >=24;
+----+---------+
| id | name |
+----+---------+
| 1 | "lucy" |
| 3 | "curry" |
+----+---------+
2 rows in set (0.00 sec)
##复杂情况下的查询，例如
mysql> select info from json_table where id=3;
+----------------------------------------------------------------+
| info |
+----------------------------------------------------------------+
| ["abc", {"xxx": [123, 456], "my key": "my value"}, [666, 100]] |
+----------------------------------------------------------------+
1 row in set (0.00 sec)
## 查询json array的某个值
mysql> select info->'$[0]' from json_table where id=3 ;
+---------------+
| info->'$[0]' |
+---------------+
| "abc" |
+---------------+
1 row in set (0.00 sec)
## 查询json array中的的json object
mysql> select info->'$[1]."my key"' from json_table where id=3 ;
+--------------------------+
| info->'$[1]."my key"' |
+--------------------------+
| "my value" |
+--------------------------+
1 row in set (0.00 sec)
JSON_EXTRACT(json列 , '$.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->>'$.name' as name from json_table ;
+----+-------+
| id | name |
+----+-------+
| 1 | lucy |
| 2 | lili |
| 3 | curry |
+----+-------+
3 rows in set (0.00 sec)
JSON字段与字符串比较举栗：
mysql> select * from json_table where info = '{"age": 25, "name": "curry"}';
Empty set (0.00 sec)
mysql> select * from json_table where info = cast('{"age": 25, "name": "curry"}' as JSON);
+----+------------------------------+
| id | info |
+----+------------------------------+
| 3 | {"age": 25, "name": "curry"} |
+----+------------------------------+
1 row in set (0.00 sec)
JSON的索引
现在MySQL不支持对JSON列进行索引，官网文档的说明是：
JSON columns cannot be indexed. You can work around this restriction by creating an index on a generated column that extracts a scalar value from the JSON column.
虽然不支持直接在JSON列上建索引，但MySQL规定，可以首先使用路径表达式对JSON文档中的标量值建立虚拟列，然后在虚拟列上建立索引。这样用户可以使用表达式对自己感兴趣的键值建立索引。
栗如，创建索引：
mysql> alter table json_table add name varchar(20) generated always as (info->'$.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)
修改
JSON_INSERT() 插入新字段，对于已存在的字段无法修改
#插入新字段
mysql> update json_table set info=json_insert(info, '$.sex', 'M');
Query OK, 6 rows affected (0.30 sec)
Rows matched: 6 Changed: 6 Warnings: 0
mysql> select * from json_table ;
+----+-----------------------------------------------------------+
| id | info |
+----+-----------------------------------------------------------+
| 1 | {"age": 24, "sex": "M", "name": "lucy"} |
| 2 | {"age": 20, "sex": "M", "name": "lili"} |
| 3 | {"age": 25, "sex": "M", "name": "curry"} |
| 4 | {"age": 24, "sex": "M", "name": "tom"} |
| 5 | {"age": 24, "sex": "M", "name": "jurry"} |
| 6 | {"age": 30, "sex": "M", "name": "tmry"} |
+----+-----------------------------------------------------------+
6 rows in set (0.00 sec)
#对于已存在的字段无法修改
mysql> update json_table set info=json_insert(info, '$.name', 'LUCY') where id=1;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1 Changed: 0 Warnings: 0
mysql> select * from json_table where id=1 ;
+----+-----------------------------------------------------------+
| id | info |
+----+-----------------------------------------------------------+
| 1 | {"age": 24, "sex": "M", "name": "lucy"} |
+----+-----------------------------------------------------------+
6 rows in set (0.00 sec)
JSON_SET() 插入新值字段，并覆盖已经存在字段的值
#覆盖已经存在字段的值
mysql> update json_table set info=json_set(info, '$.name', 'LUCY') where id=1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from json_table where id=1;
+----+-----------------------------------------------------------+
| id | info |
+----+-----------------------------------------------------------+
| 1 | {"age": 24, "sex": "M", "name": "LUCY"} |
+----+-----------------------------------------------------------+
1 row in set (0.00 sec)
#插入新值字段
mysql> update json_table set info=json_set(info, '$.class', 'python') where id=2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from json_table where id=2;
+----+------------------------------------------------------------+
| id | info |
+----+------------------------------------------------------------+
| 2 | {"age": 20, "sex": "M", "name": "lili", "class": "python"} |
+----+------------------------------------------------------------+
1 row in set (0.00 sec)
JSON_REPLACE() 只替换存在的字段
mysql> update json_table set info=json_replace(info, '$.sex', 'W') where id=2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from json_table where id = 2 ;
+----+------------------------------------------------------------+
| id | info |
+----+------------------------------------------------------------+
| 2 | {"age": 20, "sex": "W", "name": "lili", "class": "python"} |
+----+------------------------------------------------------------+
1 row in set (0.00 sec)
JSON_REMOVE() 删除 JSON 元素
mysql> update json_table set info=json_remove(info, '$.class') where id=2 ;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from json_table where id = 2 ;
+----+-----------------------------------------+
| id | info |
+----+-----------------------------------------+
| 2 | {"age": 20, "sex": "W", "name": "lili"} |
+----+-----------------------------------------+
1 row in set (0.00 sec)