时间：2021-01-10 11:07:00 | 栏目：Mysql | 点击：次
前言
因为项目需要，存储字段存储成了JSON格式，在项目中是将查询出来的值通过jackson转成相应的bean进行处理的，觉得不够简单方便。
MySQL从5.7版本开始就支持JSON格式的数据，操作用起来挺方便的。
建表
在新建表时字段类型可以直接设置为json类型，比如我们创建一张表：
mysql> CREATE TABLE `test_user`(`id` INT PRIMARY KEY AUTO_INCREMENT, `name` VARCHAR(50) NOT NULL, `info` JSON);
json类型字段可以为NULL
插入数据：
mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaoming','{"sex": 1, "age": 18, "nick_name": "小萌"}');
json类型的字段必须时一个有效的json字符串
可以使用JSON_OBJECT()函数构造json对象：
mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaohua', JSON_OBJECT("sex", 0, "age", 17));
使用JSON_ARRAY()函数构造json数组：
mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaozhang', JSON_OBJECT("sex", 1, "age", 19, "tag", JSON_ARRAY(3,5,90)));
现在查看test_user表中的数据：
mysql> select * from test_user;
+----+-----------+--------------------------------------------+
| id | name | info |
+----+-----------+--------------------------------------------+
| 1 | xiaoming | {"age": 18, "sex": 1, "nick_name": "小萌"} |
| 2 | xiaohua | {"age": 17, "sex": 0} |
| 3 | xiaozhang | {"age": 19, "sex": 1, "tag": [3, 5, 90]} |
+----+-----------+--------------------------------------------+
3 rows in set (0.04 sec)
查询
表达式： 对象为json列->'$.键', 数组为json列->'$.键[index]'
mysql> select name, info->'$.nick_name', info->'$.sex', info->'$.tag[0]' from test_user; +-----------+---------------------+---------------+------------------+ | name | info->'$.nick_name' | info->'$.sex' | info->'$.tag[0]' | +-----------+---------------------+---------------+------------------+ | xiaoming | "小萌" | 1 | NULL | | xiaohua | NULL | 0 | NULL | | xiaozhang | NULL | 1 | 3 | +-----------+---------------------+---------------+------------------+ 3 rows in set (0.04 sec)
等价于：对象为JSON_EXTRACT(json列 , '$.键') ，数组为JSON_EXTRACT(json列 , '$.键[index]')
mysql> select name, JSON_EXTRACT(info, '$.nick_name'), JSON_EXTRACT(info, '$.sex'), JSON_EXTRACT(info, '$.tag[0]') from test_user; +-----------+-----------------------------------+-----------------------------+--------------------------------+ | name | JSON_EXTRACT(info, '$.nick_name') | JSON_EXTRACT(info, '$.sex') | JSON_EXTRACT(info, '$.tag[0]') | +-----------+-----------------------------------+-----------------------------+--------------------------------+ | xiaoming | "小萌" | 1 | NULL | | xiaohua | NULL | 0 | NULL | | xiaozhang | NULL | 1 | 3 | +-----------+-----------------------------------+-----------------------------+--------------------------------+ 3 rows in set (0.04 sec)
不过看到上面"小萌"是带双引号的，这不是我们想要的，可以用JSON_UNQUOTE函数将双引号去掉
mysql> select name, JSON_UNQUOTE(info->'$.nick_name') from test_user where name='xiaoming'; +----------+-----------------------------------+ | name | JSON_UNQUOTE(info->'$.nick_name') | +----------+-----------------------------------+ | xiaoming | 小萌 | +----------+-----------------------------------+ 1 row in set (0.05 sec)
也可以直接使用操作符->>
mysql> select name, info->>'$.nick_name' from test_user where name='xiaoming'; +----------+----------------------+ | name | info->>'$.nick_name' | +----------+----------------------+ | xiaoming | 小萌 | +----------+----------------------+ 1 row in set (0.06 sec)
当然属性也可以作为查询条件
mysql> select name, info->>'$.nick_name' from test_user where info->'$.nick_name'='小萌'; +----------+----------------------+ | name | info->>'$.nick_name' | +----------+----------------------+ | xiaoming | 小萌 | +----------+----------------------+ 1 row in set (0.05 sec)
值得一提的是，可以通过虚拟列对JSON类型的指定属性进行快速查询。
创建虚拟列:
mysql> ALTER TABLE `test_user` ADD `nick_name` VARCHAR(50) GENERATED ALWAYS AS (info->>'$.nick_name') VIRTUAL;
注意用操作符->>
使用时和普通类型的列查询是一样:
mysql> select name,nick_name from test_user where nick_name='小萌'; +----------+-----------+ | name | nick_name | +----------+-----------+ | xiaoming | 小萌 | +----------+-----------+ 1 row in set (0.05 sec)
更新
使用JSON_INSERT()插入新值，但不会覆盖已经存在的值
mysql> UPDATE test_user SET info = JSON_INSERT(info, '$.sex', 1, '$.nick_name', '小花') where id=2;
看下结果
mysql> select * from test_user where id=2;
+----+---------+--------------------------------------------+-----------+
| id | name | info | nick_name |
+----+---------+--------------------------------------------+-----------+
| 2 | xiaohua | {"age": 17, "sex": 0, "nick_name": "小花"} | 小花 |
+----+---------+--------------------------------------------+-----------+
1 row in set (0.06 sec)
使用JSON_SET()插入新值，并覆盖已经存在的值
mysql> UPDATE test_user SET info = JSON_INSERT(info, '$.sex', 0, '$.nick_name', '小张') where id=3;
看下结果
mysql> select * from test_user where id=3;
+----+-----------+---------------------------------------------------------------+-----------+
| id | name | info | nick_name |
+----+-----------+---------------------------------------------------------------+-----------+
| 3 | xiaozhang | {"age": 19, "sex": 1, "tag": [3, 5, 90], "nick_name": "小张"} | 小张 |
+----+-----------+---------------------------------------------------------------+-----------+
1 row in set (0.06 sec)
使用JSON_REPLACE()只替换存在的值
mysql> UPDATE test_user SET info = JSON_REPLACE(info, '$.sex', 1, '$.tag', '[1,2,3]') where id=2;
看下结果
mysql> select * from test_user where id=2;
+----+---------+--------------------------------------------+-----------+
| id | name | info | nick_name |
+----+---------+--------------------------------------------+-----------+
| 2 | xiaohua | {"age": 17, "sex": 1, "nick_name": "小花"} | 小花 |
+----+---------+--------------------------------------------+-----------+
1 row in set (0.06 sec)
可以看到tag没有更新进去
删除
使用JSON_REMOVE()删除JSON元素
mysql> UPDATE test_user SET info = JSON_REMOVE(info, '$.sex', '$.tag') where id=1;
看下结果
mysql> select * from test_user where id=1;
+----+----------+----------------------------------+-----------+
| id | name | info | nick_name |
+----+----------+----------------------------------+-----------+
| 1 | xiaoming | {"age": 18, "nick_name": "小萌"} | 小萌 |
+----+----------+----------------------------------+-----------+
1 row in set (0.05 sec)
总结