MariaDB 10.0.X中，动态列支持 JSON 格式来获取数据

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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

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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

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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）：

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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

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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：

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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：

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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：

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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)