mysql5.7新特性JSON数据类型解析-白红宇

废话不多说，直接上实例。

一、json结构

创建测试表

                            
CREATE
TABLE
`article` (
  
`id` 
int
(11) unsigned 
NOT
NULL
AUTO_INCREMENT,
  
`category` json 
NOT
NULL
,
  
`tags` json 
NOT
NULL
,
  
PRIMARY
KEY
(`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 
DEFAULT
CHARSET=utf8
         
       

分析：article表中的字段category与tags均为json类型

填写测试数据

                            
INSERT
INTO
`article` 
VALUES
(1,
'{\"id\": 1, \"name\": \"php\"}'
,
'[\"php\", \"mysql\", \"linux\", \"nginx\", \"redis\", \"memcache\", \"mongodb\"]'
),
(2,
'{\"id\": 2, \"name\": \"java\"}'
,
'[\"java\", \"mysql\", \"oracel\", \"linux\", \"nginx\", \"redis\", \"memcache\", \"mongodb\"]'
),
(3,
'{\"id\": \"3\", \"name\": \"c#\"}'
,
'[\"c\", \"c++\", \"OS\", \"linux\", \"unix\", \"IBM\"]'
);
         
       

总体预览

二、json查询

select id,json_extract(category,'$.name') as name from test.article;#提取json字段里面的信息

# column->path形式访问json中的元素 category->'$.name'

select id,category->'$.name' as name from test.article;#提取json字段里面的信息(访问json中的元素 category->'$.name')

select id,json_unquote(json_extract(category,'$.name')) as name from test.article;#提取json字段里面的信息,json_unqoute去双引号

select id,json_unquote(category->'$.name') as name from test.article;#提取json字段里面的信息，json_unqoute去双引号

select id,category->>'$.name' as name from test.article;

select * from test.article where category='{"id": 1, "name": "php"}'; #json不同于字符串，不能当作字符串做比较

select * from test.article where category=cast('{"id": 1, "name": "php"}' as JSON); #通过CAST将字符串转换成JSON形式

select * from test.article where category->'$.name'='java';

select * from test.article where category->>'$.name'='java';

#JSON 中的元素搜索是严格区分变量类型的，比如说整型和字符串是严格区分的

select * from test.article where category->'$.id'='2';#字符号串

select * from test.article where category->'$.id'=2;#整形

select * from test.article where category->'$.id'='3';#字符号串

select * from test.article where json_extract(category,'$.id')='3';#字符号串

select * from test.article where json_contains(category,'2','$.id');#整数

select * from test.article where json_contains(category,'"3"','$.id');#字符号串

select * from test.article where json_contains(tags,'"linux"');#字符号串

2、查询json格式的字段

mysql> select jsn_extract(data, '.name′),jsnextract(data,′.address') from user;

+-----------------------------+-------------------------------+

| jsn_extract(data, '.name′)|jsnextract(data,′.address') |

+-----------------------------+-------------------------------+

| "David" | "Shangahai" |

| "Amy" | NULL |

+-----------------------------+-------------------------------+

2 rows in set (0.00 sec)

3、给json格式的某个键字段创建索引。首先创建虚拟列，之后在改虚拟列上创建索引。

mysql> ALTER TABLE user ADD user_name varchar(128)

-> GENERATED ALWAYS AS (jsn_extract(data,'$.name')) VIRTUAL;

Query OK, 0 rows affected (0.01 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> select user_name from user;

+-----------+

| user_name |

+-----------+

| "Amy" |

| "David" |

+-----------+

2 rows in set (0.00 sec)

mysql> alter table user add index idx_username (user_name);

Query OK, 2 rows affected (0.01 sec)

Records: 2 Duplicates: 0 Warnings: 0

4、之后通过虚拟列名对json特定列进行索引查询：

mysql> explain select * from user where user_name='"Amy"'\G

*************************** 1. row ***************************

id: 1

select_type: SIMPLE

table: user

partitions: NULL

type: ref

possible_keys: idx_username

key: idx_username

key_len: 131

ref: const

rows: 1

filtered: 100.00

Extra: NULL

1 row in set, 1 warning (0.00 sec)

三、json更新

更新 JSON

如果是整个 json 更新的话，和插入时类似的。

mysql> UPDATE lnmp SET tags = '[1, 3, 4]' WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM lnmp;+----+------------------------------+-----------+ | id | category                     | tags      | +----+------------------------------+-----------+ | 1  | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] | | 2  | {"id": 2, "name": "php.net"} | [1, 3, 5] |+----+------------------------------+-----------+2 rows in set (0.00 sec)

但如果要更新 JSON 下的元素，MySQL 并不支持 column->path 的形式

mysql> UPDATE lnmp SET category->'$.name' = 'lnmp', tags->'$[0]' = 2 WHERE id = 1;
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 '->'$.name' = 'lnmp', tags->'$[0]' = 2 WHERE id = 1' at line 1

则可能要用到以下几个函数

JSON_INSERT() 插入新值，但不会覆盖已经存在的值

mysql> UPDATE lnmp SET category = JSON_INSERT(category, '$.name', 'lnmp', '$.url', 'www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM lnmp;+----+----------------------------------------------------+-----------+| id | category                                           | tags      |+----+----------------------------------------------------+-----------+|  1 | {"id": 1, "url": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] ||  2 | {"id": 2, "name": "php.net"}                       | [1, 3, 5] |+----+----------------------------------------------------+-----------+2 rows in set (0.00 sec)

可以看到 name 没有被修改，但新元素 url 已经添加进去

JSON_SET() 插入新值，并覆盖已经存在的值

mysql> UPDATE lnmp SET category = JSON_SET(category, '$.host', 'www.lnmp.cn', '$.url', 'http://www.lnmp.cn') WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM lnmp;+----+----------------------------------------------------------------------------------+-----------+| id | category                                                                         | tags      |+----+----------------------------------------------------------------------------------+-----------+|  1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] ||  2 | {"id": 2, "name": "php.net"}                                                     | [1, 3, 5] |+----+----------------------------------------------------------------------------------+-----------+2 rows in set (0.00 sec)

可以看到 host 已经插入，url 已经被修改

JSON_REPLACE() 只替换存在的值

mysql> UPDATE lnmp SET category = JSON_REPLACE(category, '$.name', 'php', '$.url', 'http://www.php.net') WHERE id = 2;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM lnmp;+----+----------------------------------------------------------------------------------+-----------+| id | category                                                                         | tags      |+----+----------------------------------------------------------------------------------+-----------+|  1 | {"id": 1, "url": "http://www.lnmp.cn", "host": "www.lnmp.cn", "name": "lnmp.cn"} | [1, 3, 4] ||  2 | {"id": 2, "name": "php"}                                                         | [1, 3, 5] |+----+----------------------------------------------------------------------------------+-----------+2 rows in set (0.00 sec)

可以看到 name 已经被替换，url 不存在被忽略。

JSON_REMOVE() 删除 JSON 元素

mysql> UPDATE lnmp SET category = JSON_REMOVE(category, '$.url', '$.host') WHERE id = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT * FROM lnmp;+----+------------------------------+-----------+| id | category                     | tags      |+----+------------------------------+-----------+|  1 | {"id": 1, "name": "lnmp.cn"} | [1, 3, 4] ||  2 | {"id": 2, "name": "php"}     | [1, 3, 5] |+----+------------------------------+-----------+2 rows in set (0.00 sec)

更多函数请参考：

MySQL JSON 在 PHP 中的表现

虽然在 MySQL 是个JSON 类型，但实际在 PHP 应用中返回的是 JSON 格式的字符串

array(2) {  [0]=>  array(3) {    ["id"]=>    string(1) "1"    ["category"]=>    string(28) "{"id": 1, "name": "lnmp.cn"}"    ["tags"]=>    string(9) "[1, 3, 4]"  }  [1]=>  array(3) {    ["id"]=>    string(1) "2"    ["category"]=>    string(24) "{"id": 2, "name": "php"}"    ["tags"]=>    string(9) "[1, 3, 5]"  }}

本文转自 hgditren 51CTO博客，原文链接：http://blog.51cto.com/phpme/2057161，如需转载请自行联系原作者