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  • MySQL系列 | MySQL5.7特性:JSON数据类型 [转载]

    概述

    MySQL5.7的发行声明中,官方称之为里程碑式的版本,除了运行速度大幅度提升之外,还添加了之前版本没有的功能,如本文所述的原生JSON数据类型功能。
    在此版本之前,MySQL所有的JSON数据类型,全部是使用text等文本类型来实现的,数据的处理只能在应用代码级来实现,十分不方便。

    什么是JSON类型

    作为DBA,可能会对这个概念稍微有点陌生,但是对于开发者来说,这是一个十分熟悉的事物。

    JSON(JavaScript Object Notation, JS 对象简谱) 是一种轻量级的数据交换格式。它基于 ECMAScript (欧洲计算机协会制定的js规范)的一个子集,采用完全独立于编程语言的文本格式来存储和表示数据。简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。 易于人阅读和编写,同时也易于机器解析和生成,并有效地提升网络传输效率。

    MySQL原始JSON类型的优势在哪?

    原生的JSON优势如下:

    1. 存储上类似text,可以存非常大的数据。
    2. 存储在JSON列中的JSON文档的自动验证 。无效的文档会产生错误。
    3. 优化的存储格式。存储在JSON列中的JSON文档将 转换为内部格式,以允许对文档元素进行快速读取访问。
    4. 相比于传统形式,不需要遍历所有字符串才能找到数据。
    5. 支持索引:通过虚拟列的功能可以对JSON中部分的数据进行索引。

    MySQL的JSON类型

    创建JSON类型表

    创建一个基础的员工表,除了工号字段外,还有一个个人基础信息字段和一个个人能力信息字段

    MySQL [test]> CREATE TABLE  employee (
        -> 
        ->     `empno` int(10) unsigned NOT NULL AUTO_INCREMENT,
        -> 
        ->     `basic_info` JSON NOT NULL,
        -> 
        ->     `skill_info` JSON NOT NULL,
        -> 
        ->     PRIMARY KEY (`empno`)
        -> 
        -> );
    Query OK, 0 rows affected (0.02 sec)

    表的基础信息,其中JSON类型的字段,是不可以有默认值的,这点需要注意

    MySQL [test]> desc employee;
    +------------+------------------+------+-----+---------+----------------+
    | Field      | Type             | Null | Key | Default | Extra          |
    +------------+------------------+------+-----+---------+----------------+
    | empno      | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
    | basic_info | json             | NO   |     | NULL    |                |
    | skill_info | json             | NO   |     | NULL    |                |
    +------------+------------------+------+-----+---------+----------------+
    3 rows in set (0.00 sec)

    试着插入几条数据

    我们手动插入几条数据进这张表中,在前两条数据中,在个人能力信息上使用的是数组的方式,,后面两条则是使用对象的形式。在MySQL5.7.8版本后的JSON类型中,这两种都是可以的

    INSERT INTO `employee`  VALUES (1,'{"name": "wangyiyi", "age": "23" ,"from": "hangzhou"}', '["java", "go", "python"]');
    
    INSERT INTO `employee`  VALUES (2,'{"name": "linxue", "age": 24 ,"from": "shanghai"}', '["mysql", "oracle", "python"]');
    
    INSERT INTO `employee`  VALUES (3,'{"name": "zhaoqing", "age": 24 ,"from": "shanghai"}', '{"system": "linux","database": "mysql", "language": "python"}');
    
    INSERT INTO `employee`  VALUES (4,'{"name": "zhouxixi", "age": 30 ,"from": "nanjing"}', '{"system": ["linux","windows"],"database": ["mysql","oracle","postgresql"], "language": ["python","java","go"]}');

    插入多个数据后,表中内容为如下

    MySQL [test]> select * from employee;
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    | empno | basic_info                                            | skill_info                                                                                                            |
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    |     1 | {"age": "23", "from": "hangzhou", "name": "wangyiyi"} | ["java", "go", "python"]                                                                                              |
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"}     | ["mysql", "oracle", "python"]                                                                                         |
    |     3 | {"age": 24, "from": "shanghai", "name": "zhaoqing"}   | {"system": "linux", "database": "mysql", "language": "python"}                                                        |
    |     4 | {"age": 30, "from": "nanjing", "name": "zhouxixi"}    | {"system": ["linux", "windows"], "database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]} |
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    4 rows in set (0.00 sec)

    更新数据

    UPDATE resty_user SET basic_info='{"age": "23","moblie": "13669361999", "email": "tinywan@aliyun.com", "id_card": "620000988221230198",  "from": "甘肃兰州", "name": "王玉玺"}',
    skill_info='{"system": ["linux", "windows"],"database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]}' where id = 120

    json数据查询方式

    在插入了json类型的数据之后,可以针对JSON类型做一些特定的查询,如查询年龄大于20的记录
    在SQL的语句中使用 字段->.键名 就可以查询出所对应的键值

    MySQL [test]>  select * from employee  WHERE basic_info->'$.age'> 20;
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    | empno | basic_info                                            | skill_info                                                                                                            |
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    |     1 | {"age": "23", "from": "hangzhou", "name": "wangyiyi"} | ["java", "go", "python"]                                                                                              |
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"}     | ["mysql", "oracle", "python"]                                                                                         |
    |     3 | {"age": 28, "from": "shanghai", "name": "zhaoqing"}   | {"system": "linux", "database": "mysql", "language": "go"}                                                            |
    |     4 | {"age": 30, "from": "nanjing", "name": "zhouxixi"}    | {"system": ["linux", "windows"], "database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]} |
    +-------+-------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------+
    4 rows in set (0.00 sec)
    
    MySQL [test]> select * from employee  WHERE basic_info->'$.age'< 20;
    Empty set (0.00 sec)

    除了使用上述方式外,也可使用 提取json值的 函数 json_extract (使用函数的方式)

    MySQL [test]> select * from employee where json_extract(basic_info,'$.age') = 24;
    +-------+-----------------------------------------------------+----------------------------------------------------------------+
    | empno | basic_info                                          | skill_info                                                     |
    +-------+-----------------------------------------------------+----------------------------------------------------------------+
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"}   | ["mysql", "oracle", "python"]                                  |
    |     3 | {"age": 24, "from": "shanghai", "name": "zhaoqing"} | {"system": "linux", "database": "mysql", "language": "python"} |
    +-------+-----------------------------------------------------+----------------------------------------------------------------+
    2 rows in set (0.00 sec)

    对于数值查询也可做一个范围内查询,如下:

    MySQL [test]> select * from employee  WHERE basic_info->'$.age' in (23, 24);
    +-------+-------------------------------------------------------+----------------------------------------------------------------+
    | empno | basic_info                                            | skill_info                                                     |
    +-------+-------------------------------------------------------+----------------------------------------------------------------+
    |     1 | {"age": "23", "from": "hangzhou", "name": "wangyiyi"} | ["java", "go", "python"]                                       |
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"}     | ["mysql", "oracle", "python"]                                  |
    |     3 | {"age": 24, "from": "shanghai", "name": "zhaoqing"}   | {"system": "linux", "database": "mysql", "language": "python"} |
    +-------+-------------------------------------------------------+----------------------------------------------------------------+
    3 rows in set, 1 warning (0.00 sec)

    因为 JSON 不同于字符串,所以如果用字符串和 JSON 字段比较,是不会相等的:

    如下,直接使用字符串查询,查询不出来内容

    MySQL [test]> select * from employee where basic_info = '{"age": 24, "from": "shanghai", "name": "linxue"}';
    Empty set (0.00 sec)

    可以通过 CAST 将字符串转成 JSON 的形式,如下:

    MySQL [test]> select * from employee where basic_info = CAST('{"age": 24, "from": "shanghai", "name": "linxue"}' AS JSON);
    +-------+---------------------------------------------------+-------------------------------+
    | empno | basic_info                                        | skill_info                    |
    +-------+---------------------------------------------------+-------------------------------+
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"} | ["mysql", "oracle", "python"] |
    +-------+---------------------------------------------------+-------------------------------+
    1 row in set (0.00 sec)

    查看单纯数组类型的函数JSON_CONTAINS

    MySQL [test]> select * from employee where JSON_CONTAINS (skill_info,'"mysql"');
    +-------+---------------------------------------------------+-------------------------------+
    | empno | basic_info                                        | skill_info                    |
    +-------+---------------------------------------------------+-------------------------------+
    |     2 | {"age": 24, "from": "shanghai", "name": "linxue"} | ["mysql", "oracle", "python"] |
    +-------+---------------------------------------------------+-------------------------------+
    1 row in set (0.00 sec)

    JSON_PRETTY函数: 以易于阅读的格式打印出JSON值
    便于在一些外部应用引用数据时,更方便的使用它

    MySQL [test]> select JSON_PRETTY(basic_info) from employee;
    +---------------------------------------------------------------+
    | JSON_PRETTY(basic_info)                                       |
    +---------------------------------------------------------------+
    | {
      "age": "23",
      "from": "hangzhou",
      "name": "wangyiyi"
    } |
    | {
      "age": 24,
      "from": "shanghai",
      "name": "linxue"
    }     |
    | {
      "age": 28,
      "from": "shanghai",
      "name": "zhaoqing"
    }   |
    | {
      "age": 30,
      "from": "nanjing",
      "name": "zhouxixi"
    }    |
    +---------------------------------------------------------------+
    4 rows in set (0.00 sec)

    MySQL 5.7.22中添加了此功能,此函数返回用于存储JSON文档的二进制表示的字节数,用于查看当前JSON字段的存储大小

    MySQL [test]> select skill_info,JSON_STORAGE_SIZE(skill_info) AS Size  from employee;
    +-----------------------------------------------------------------------------------------------------------------------+------+
    | skill_info                                                                                                            | Size |
    +-----------------------------------------------------------------------------------------------------------------------+------+
    | ["java", "go", "python"]                                                                                              |   29 |
    | ["mysql", "oracle", "python"]                                                                                         |   34 |
    | {"system": "linux", "database": "mysql", "language": "go"}                                                            |   63 |
    | {"system": ["linux", "windows"], "database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]} |  137 |
    +-----------------------------------------------------------------------------------------------------------------------+------+
    4 rows in set (0.00 sec)

    查询JSON字段的长度

    MySQL [test]> select JSON_LENGTH(basic_info) from employee;
    +-------------------------+
    | JSON_LENGTH(basic_info) |
    +-------------------------+
    |                       3 |
    |                       3 |
    |                       3 |
    |                       3 |
    +-------------------------+
    4 rows in set (0.00 sec)

    查看数据的类型:可以是对象,数组或标量类型

    MySQL [test]> select JSON_TYPE(skill_info) from employee;
    +-----------------------+
    | JSON_TYPE(skill_info) |
    +-----------------------+
    | ARRAY                 |
    | ARRAY                 |
    | OBJECT                |
    | OBJECT                |
    +-----------------------+
    4 rows in set (0.00 sec)

    json数据修改方式

    如果是整个 json 更新的话,和一般类型插入是一样的

    json_array_insert是在指定下标插入,这是插入一般数组类型时的操作

    MySQL [test]> SELECT json_array_insert(skill_info, '$[1]', 'php') from employee;
    +-----------------------------------------------------------------------------------------------------------------------+
    | json_array_insert(skill_info, '$[1]', 'php')                                                                          |
    +-----------------------------------------------------------------------------------------------------------------------+
    | ["java", "php", "go", "python"]                                                                                       |
    | ["mysql", "php", "oracle", "python"]                                                                                  |
    | {"system": "linux", "database": "mysql", "language": "python"}                                                        |
    | {"system": ["linux", "windows"], "database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]} |
    +-----------------------------------------------------------------------------------------------------------------------+
    4 rows in set (0.00 sec)

    替换操作,也就是修改update操作,使用的是 json_replace 函数
    json_replace:只替换已经存在的旧值,不存在则忽略;

    MySQL [test]> update employee set  skill_info = json_replace(skill_info, "$.language", "go") where empno = 3;
    Query OK, 1 row affected (0.00 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    
    MySQL [test]> select * from employee where empno = 3;
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    | empno | basic_info                                          | skill_info                                                 |
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    |     3 | {"age": 24, "from": "shanghai", "name": "zhaoqing"} | {"system": "linux", "database": "mysql", "language": "go"} |
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    1 row in set (0.00 sec)

    json_set:替换旧值,并插入不存在的新值;

    MySQL [test]> update employee set  basic_info = json_set(basic_info, "$.age", 28,"$.sex" ,"man") where empno = 3;
    Query OK, 1 row affected (0.01 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    
    MySQL [test]> 
    MySQL [test]> select * from employee where empno = 3;
    +-------+-------------------------------------------------------------------+------------------------------------------------------------+
    | empno | basic_info                                                        | skill_info                                                 |
    +-------+-------------------------------------------------------------------+------------------------------------------------------------+
    |     3 | {"age": 28, "sex": "man", "from": "shanghai", "name": "zhaoqing"} | {"system": "linux", "database": "mysql", "language": "go"} |
    +-------+-------------------------------------------------------------------+------------------------------------------------------------+
    1 row in set (0.00 sec)

    json_insert:插入新值,但不替换已经存在的旧值;

    MySQL [test]> update  employee  set  basic_info = json_insert (basic_info, "$.age", 30, "$.phone" ,"123456789") where empno = 3;
    Query OK, 1 row affected (0.01 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    
    MySQL [test]> select * from employee where empno = 3;
    +-------+-----------------------------------------------------------------------------------------+------------------------------------------------------------+
    | empno | basic_info                                                                              | skill_info                                                 |
    +-------+-----------------------------------------------------------------------------------------+------------------------------------------------------------+
    |     3 | {"age": 28, "sex": "man", "from": "shanghai", "name": "zhaoqing", "phone": "123456789"} | {"system": "linux", "database": "mysql", "language": "go"} |
    +-------+-----------------------------------------------------------------------------------------+------------------------------------------------------------+
    1 row in set (0.00 sec)

    json_remove() 删除元素函数。

    MySQL [test]> update  employee  set  basic_info = json_remove (basic_info, "$.sex", "$.phone") where empno = 3;
    Query OK, 1 row affected (0.01 sec)
    Rows matched: 1  Changed: 1  Warnings: 0
    
    MySQL [test]> 
    MySQL [test]> select * from employee where empno = 3;
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    | empno | basic_info                                          | skill_info                                                 |
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    |     3 | {"age": 28, "from": "shanghai", "name": "zhaoqing"} | {"system": "linux", "database": "mysql", "language": "go"} |
    +-------+-----------------------------------------------------+------------------------------------------------------------+
    1 row in set (0.00 sec)

    结语

    JSON数据类型是一个对开发十分友好的功能,有了它,MySQL的功能才更趋于完善。

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  • 原文地址:https://www.cnblogs.com/tinywan/p/12408009.html
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