MariaDB10.0.X中，动态列支持JSON格式来获取数据。

MariaDB 10.0.X中，动态列（Dynamic Columns），可以支持 JSON 格式来获取数据。 为了兼容传统SQL语法，MariaDB 10和MySQL5.7支持原生JSON格式， 即关系型数据库和文档型NoSQL数据库集于一身 。 使用说明： ###表结构 createtableassets(item_namevarchar(32

mariadb 10.0.x中，动态列（dynamic columns），可以支持 json 格式来获取数据。

为了兼容传统SQL语法，MariaDB 10和MySQL5.7支持原生JSON格式，即关系型数据库和文档型NoSQL数据库集于一身。

使用说明：

###表结构

create table assets (
  item_name varchar(32) primary key, -- A common attribute for all items
  dynamic_cols  blob  -- Dynamic columns will be stored here
);

###插入JSON格式数据

mysql> INSERT INTO assets VALUES 
    ->   ('MariaDB T-shirt', COLUMN_CREATE('color', 'blue', 'size', 'XL'));
Query OK, 1 row affected (0.02 sec)

mysql> INSERT INTO assets VALUES
    ->   ('Thinkpad Laptop', COLUMN_CREATE('color', 'black', 'price', 500));
Query OK, 1 row affected (0.01 sec)

###获取Key（键）color的Value（值）：

mysql> SELECT item_name, COLUMN_GET(dynamic_cols, 'color' as char) AS color FROM assets;
+-----------------+-------+
| item_name       | color |
+-----------------+-------+
| MariaDB T-shirt | blue  |
| Thinkpad Laptop | black |
+-----------------+-------+
2 rows in set (0.00 sec)

###获取全部Key（键）

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mysql> SELECT item_name, column_list(dynamic_cols) FROM assets;
+-----------------+---------------------------+
| item_name       | column_list(dynamic_cols) |
+-----------------+---------------------------+
| MariaDB T-shirt | `size`,`color`            |
| Thinkpad Laptop | `color`,`price`           |
+-----------------+---------------------------+
2 rows in set (0.00 sec)

###获取全部Key-Value

mysql> SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;
+-----------------+-------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)     |
+-----------------+-------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}  |
| Thinkpad Laptop | {"color":"black","price":500} |
+-----------------+-------------------------------+
2 rows in set (0.01 sec)

###删除一个Key-Value：

mysql> UPDATE assets SET dynamic_cols=COLUMN_DELETE(dynamic_cols, "price") 
    -> WHERE COLUMN_GET(dynamic_cols, 'color' as char)='black';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;
+-----------------+------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)    |
+-----------------+------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"} |
| Thinkpad Laptop | {"color":"black"}            |
+-----------------+------------------------------+
2 rows in set (0.00 sec)

###增加一个Key-Value：

mysql> UPDATE assets SET dynamic_cols=COLUMN_ADD(dynamic_cols, 'warranty', '3 years')
    -> WHERE item_name='Thinkpad Laptop';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;                            
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"black","warranty":"3 years"} |
+-----------------+----------------------------------------+
2 rows in set (0.00 sec)

###更改一个Key-Value：

mysql> UPDATE assets SET 
dynamic_cols=COLUMN_ADD(dynamic_cols,'color', 'white') WHERE 
COLUMN_GET(dynamic_cols, 'color' as char)='black';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"white","warranty":"3 years"} |
+-----------------+----------------------------------------+
2 rows in set (0.00 sec)