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MySQL 5.7原生JSON格式支持

MySQL 5.7原生JSON格式支持:

mysql> create table user ( uid int auto_increment,  -> data json,primary key(uid))engine=innodb; Query OK, 0 rows affected (0.01 sec) mysql> insert into user values (NULL,  -> '{"name":"David","mail":"jiangchengyao@gmail.com","address":"Shangahai"}'); Query OK, 1 row affected (0.00 sec) mysql> insert into user values (NULL,'{"name":"Amy","mail":"amy@gmail.com"}'); Query OK, 1 row affected (0.00 sec) 

可以看到我们新建了表user,并且将列data定义为了JSON类型。这意味着我们可以对插入的数据做JSON格式检查,确保其符合JSON格式的约束,如插入一条不合法的JSON数据会报如下错误:

mysql> insert into user values (NULL,"test");

ERROR 3130 (22032): Invalid JSON text: "Invalid value" at position 2 in value (or column) 'test'.

此外,正如前面所说的,MySQL 5.7提供了一系列函数来高效地处理JSON字符,而不是需要遍历所有字符来查找,这不得不说是对MariaDB dynamic column的巨大改进:

mysql> select jsn_extract(data, '$.name'),jsn_extract(data,'$.address') from user; +-----------------------------+-------------------------------+ | jsn_extract(data, '$.name') | jsn_extract(data,'$.address') | +-----------------------------+-------------------------------+ | "David" | "Shangahai" | | "Amy" | NULL | +-----------------------------+-------------------------------+ 2 rows in set (0.00 sec)

当然,最令人的激动的功能应该是MySQL 5.7的虚拟列功能,通过传统的B+树索引即可实现对JSON格式部分属性的快速查询。使用方法是首先创建该虚拟列,然后在该虚拟列上创建索引:

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 

然后可以通过添加的索引对用户名进行快速的查询,这和普通类型的列查询一样。而通过explain可以验证优化器已经选择了在虚拟列上创建的新索引:

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)

可以发现MySQL 5.7对于JSON格式堪称完美

摘自:http://www.innomysql.net/article/15319.html

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