MySQL系列 | MySQL5.7特性：JSON數據類型 [轉載]

概述

MySQL5.7的發行聲明中，官方稱之爲里程碑式的版本，除了運行速度大幅度提升之外，還添加了之前版本沒有的功能，如本文所述的原生JSON數據類型功能。
在此版本之前，MySQL所有的JSON數據類型，全部是使用text等文本類型來實現的，數據的處理只能在應用代碼級來實現，十分不方便。

什麼是JSON類型

作爲DBA，可能會對這個概念稍微有點陌生，但是對於開發者來說，這是一個十分熟悉的事物。

JSON(JavaScript Object Notation, JS 對象簡譜) 是一種輕量級的數據交換格式。它基於 ECMAScript (歐洲計算機協會制定的js規範)的一個子集，採用完全獨立於編程語言的文本格式來存儲和表示數據。簡潔和清晰的層次結構使得 JSON 成爲理想的數據交換語言。易於人閱讀和編寫，同時也易於機器解析和生成，並有效地提升網絡傳輸效率。

MySQL原始JSON類型的優勢在哪？

原生的JSON優勢如下：

存儲上類似text,可以存非常大的數據。
存儲在JSON列中的JSON文檔的自動驗證。無效的文檔會產生錯誤。
優化的存儲格式。存儲在JSON列中的JSON文檔將轉換爲內部格式，以允許對文檔元素進行快速讀取訪問。
相比於傳統形式，不需要遍歷所有字符串才能找到數據。
支持索引：通過虛擬列的功能可以對JSON中部分的數據進行索引。

MySQL的JSON類型

創建JSON類型表

創建一個基礎的員工表，除了工號字段外，還有一個個人基礎信息字段和一個個人能力信息字段

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)

表的基礎信息，其中JSON類型的字段，是不可以有默認值的，這點需要注意

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)

試着插入幾條數據

我們手動插入幾條數據進這張表中，在前兩條數據中，在個人能力信息上使用的是數組的方式，，後面兩條則是使用對象的形式。在MySQL5.7.8版本後的JSON類型中，這兩種都是可以的

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"]}');

插入多個數據後,表中內容爲如下

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)

更新數據

UPDATE resty_user SET basic_info='{"age": "23","moblie": "13669361999", "email": "[email protected]", "id_card": "620000988221230198",  "from": "甘肅蘭州", "name": "王玉璽"}',
skill_info='{"system": ["linux", "windows"],"database": ["mysql", "oracle", "postgresql"], "language": ["python", "java", "go"]}' where id = 120

json數據查詢方式

在插入了json類型的數據之後，可以針對JSON類型做一些特定的查詢，如查詢年齡大於20的記錄
在SQL的語句中使用字段->.鍵名就可以查詢出所對應的鍵值

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值的函數 json_extract （使用函數的方式）

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)

對於數值查詢也可做一個範圍內查詢，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)

因爲 JSON 不同於字符串，所以如果用字符串和 JSON 字段比較，是不會相等的：

如下，直接使用字符串查詢，查詢不出來內容

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

可以通過 CAST 將字符串轉成 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)

查看單純數組類型的函數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函數：以易於閱讀的格式打印出JSON值
便於在一些外部應用引用數據時，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，此函數返回用於存儲JSON文檔的二進制表示的字節數，用於查看當前JSON字段的存儲大小

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)

查詢JSON字段的長度

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

查看數據的類型：可以是對象，數組或標量類型

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數據修改方式

如果是整個 json 更新的話，和一般類型插入是一樣的

json_array_insert是在指定下標插入，這是插入一般數組類型時的操作

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)

替換操作，也就是修改update操作，使用的是 json_replace 函數
json_replace：只替換已經存在的舊值，不存在則忽略；

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：替換舊值，並插入不存在的新值；

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，但不替換已經存在的舊值；

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() 刪除元素函數。

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)

結語

JSON數據類型是一個對開發十分友好的功能，有了它，MySQL的功能才更趨於完善。

MySQL系列 | MySQL5.7特性：JSON數據類型 [轉載]

概述

什麼是JSON類型

MySQL的JSON類型

創建JSON類型表

試着插入幾條數據

更新數據

json數據查詢方式

json數據修改方式

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