MySQL 5.7新支持--------Json类型实战

1. 背景
　 * 在MySQL 5.7.8中，MySQL支持由RFC 7159定义的本地JSON数据类型，它支持对JSON(JavaScript对象标记)文档中的数据进行有效访问.
　 * MySQL会对DML JSON数据自动验证。无效的DML JSON数据操作会产生错误.
* 优化的存储格式。存储在JSON列中的JSON文档转换为一种内部格式，允许对Json元素进行快速读取访问.
* MySQL Json类型支持建立索引增加查询性能提升.

2. Json类型所需的存储空间和值范围

类型	占用字节	最大长度
Json	数据长度 + 4 bytes	4G

3. Json相关函数操作
* JSON_OBJECT(string1, string2...) 创建 key-value 类型 Json 对象

mysql> SELECT JSON_OBJECT('k1', 'v1', 'k2', 'v2');
+-------------------------------------+
| JSON_OBJECT('k1', 'v1', 'k2', 'v2') |
+-------------------------------------+
| {"k1": "v1", "k2": "v2"}            |
+-------------------------------------+
1 row in set (0.01 sec)

* JSON_ARRAY(string1, string2...) 创建一个 Json 数组

mysql> SELECT JSON_ARRAY('a', 'b', 'c', 'd');
+--------------------------------+
| JSON_ARRAY('a', 'b', 'c', 'd') |
+--------------------------------+
| ["a", "b", "c", "d"]           |
+--------------------------------+
1 row in set (0.00 sec)

* JSON_TYPE(object) 判断并显示数据类型 [ 值非法会报错显示 ]

mysql>  SELECT JSON_TYPE('"lisea"');
+----------------------+
| JSON_TYPE('"lisea"') |
+----------------------+
| STRING               |
+----------------------+
1 row in set (0.01 sec)

mysql> SELECT JSON_TYPE('["a", "b", 1]');
+----------------------------+
| JSON_TYPE('["a", "b", 1]') |
+----------------------------+
| ARRAY                      |
+----------------------------+
1 row in set (0.01 sec)

mysql> SELECT JSON_TYPE('1');
+----------------+
| JSON_TYPE('1') |
+----------------+
| INTEGER        |
+----------------+
1 row in set (0.00 sec)

mysql> SELECT JSON_TYPE('{"k1":"v1", "k2":"v2"}');
+-------------------------------------+
| JSON_TYPE('{"k1":"v1", "k2":"v2"}') |
+-------------------------------------+
| OBJECT                              |
+-------------------------------------+
1 row in set (0.00 sec)

* JSON_MERGE(doc1,doc2....) 合并多个Json对象

mysql> SELECT JSON_MERGE('{"k1":"v1"}','{ "k2":"v2"}');
+------------------------------------------+
| JSON_MERGE('{"k1":"v1"}','{ "k2":"v2"}') |
+------------------------------------------+
| {"k1": "v1", "k2": "v2"}                 |
+------------------------------------------+
1 row in set (0.04 sec)

mysql> SELECT JSON_MERGE('["k1","k2"]','{ "k3":"v3"}');
+------------------------------------------+
| JSON_MERGE('["k1","k2"]','{ "k3":"v3"}') |
+------------------------------------------+
| ["k1", "k2", {"k3": "v3"}]               |
+------------------------------------------+
1 row in set (0.00 sec)

* JSON_EXTRACT(object, key) 通过Json key方式获取Val值

mysql> SELECT JSON_EXTRACT('{"k1":"v1","k2":"v2"}', '$.k1');
+-----------------------------------------------+
| JSON_EXTRACT('{"k1":"v1","k2":"v2"}', '$.k1') |
+-----------------------------------------------+
| "v1"                                          |
+-----------------------------------------------+
1 row in set (0.01 sec)

mysql> SELECT JSON_EXTRACT('{"k1":"v1","k2":"v2"}', '$.*');
+----------------------------------------------+
| JSON_EXTRACT('{"k1":"v1","k2":"v2"}', '$.*') |
+----------------------------------------------+
| ["v1", "v2"]                                 |
+----------------------------------------------+
1 row in set (0.00 sec)

* JSON_SET(object, key, val, key, val....) 通过key修改val值

mysql> SELECT JSON_SET('{"k1":"v1","k2":"v2"}', '$.k1', 'lisea', '$.k2', 'hello');
+---------------------------------------------------------------------+
| JSON_SET('{"k1":"v1","k2":"v2"}', '$.k1', 'lisea', '$.k2', 'hello') |
+---------------------------------------------------------------------+
| {"k1": "lisea", "k2": "hello"}                                      |
+---------------------------------------------------------------------+
1 row in set (0.00 sec)

* JSON_INSERT(object, key, val)添加新值到对象中，如果key已存在，不替换val

mysql> SELECT JSON_INSERT('{"k1":"v1","k2":"v2"}', '$.k1', 'hello');
+-------------------------------------------------------+
| JSON_INSERT('{"k1":"v1","k2":"v2"}', '$.k1', 'hello') |
+-------------------------------------------------------+
| {"k1": "v1", "k2": "v2"}                              |
+-------------------------------------------------------+
1 row in set (0.03 sec)

mysql> SELECT JSON_INSERT('{"k1":"v1","k2":"v2"}', '$.k3', 'v3');
+----------------------------------------------------+
| JSON_INSERT('{"k1":"v1","k2":"v2"}', '$.k3', 'v3') |
+----------------------------------------------------+
| {"k1": "v1", "k2": "v2", "k3": "v3"}               |
+----------------------------------------------------+
1 row in set (0.02 sec)

* JSON_REPLACE() 替换现有的值并忽略新的值

mysql> SELECT JSON_REPLACE('{"k1":"v1","k2":"v2"}', '$.k1', 'hello', '$.k3', 'v3');
+----------------------------------------------------------------------+
| JSON_REPLACE('{"k1":"v1","k2":"v2"}', '$.k1', 'hello', '$.k3', 'v3') |
+----------------------------------------------------------------------+
| {"k1": "hello", "k2": "v2"}                                          |
+----------------------------------------------------------------------+
1 row in set (0.01 sec)

* JSON_REMOVE() 通过key移除

mysql> SELECT JSON_REMOVE('{"k1":"v1","k2":"v2"}', '$.k1');
+----------------------------------------------+
| JSON_REMOVE('{"k1":"v1","k2":"v2"}', '$.k1') |
+----------------------------------------------+
| {"k2": "v2"}                                 |
+----------------------------------------------+
1 row in set (0.00 sec)

* JSON_KEYS() 获取所有key

mysql> SELECT JSON_KEYS('{"k1":"v1","k2":"v2"}');
+------------------------------------+
| JSON_KEYS('{"k1":"v1","k2":"v2"}') |
+------------------------------------+
| ["k1", "k2"]                       |
+------------------------------------+
1 row in set (0.03 sec)

* JSON_UNQUOTE() 去掉值的引号

mysql> SELECT JSON_UNQUOTE('"hello"');
+-------------------------+
| JSON_UNQUOTE('"hello"') |
+-------------------------+
| hello                   |
+-------------------------+
1 row in set (0.01 sec)

* JSON_DEPTH() 获取Json对象的深度

mysql> SELECT JSON_DEPTH('{"k1":"v1","k2":"v2"}');
+-------------------------------------+
| JSON_DEPTH('{"k1":"v1","k2":"v2"}') |
+-------------------------------------+
|                                   2 |
+-------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT JSON_DEPTH('{}');
+------------------+
| JSON_DEPTH('{}') |
+------------------+
|                1 |
+------------------+
1 row in set (0.01 sec)

* JSON_VALID() 判断是否为有效的json格式

mysql> SELECT JSON_VALID('{"k1":"v1"}');
+---------------------------+
| JSON_VALID('{"k1":"v1"}') |
+---------------------------+
|                         1 |
+---------------------------+
1 row in set (0.00 sec)

mysql> SELECT JSON_VALID('{"k1":"v1"');
+--------------------------+
| JSON_VALID('{"k1":"v1"') |
+--------------------------+
|                        0 |
+--------------------------+
1 row in set (0.00 sec)

* JSON_LENGTH() 获取指定路径下的长度
长度的计算规则:
标量的长度为1
json array的长度为元素的个数
json object的长度为key的个数

mysql> SELECT JSON_LENGTH('[1, 2, 3]');
+--------------------------+
| JSON_LENGTH('[1, 2, 3]') |
+--------------------------+
|                        3 |
+--------------------------+
1 row in set (0.00 sec)

mysql> SELECT JSON_LENGTH('{"k1":"v1", "k2":"v2"}');
+---------------------------------------+
| JSON_LENGTH('{"k1":"v1", "k2":"v2"}') |
+---------------------------------------+
|                                     2 |
+---------------------------------------+
1 row in set (0.00 sec)

* JSON_SEARCH(json_doc, one_or_all, search_str[, escape_char[, path] ...])
　　　查询包含指定字符串的paths，并作为一个json array返回　
　　　one_or_all："one"表示查询到一个即返回；"all"表示查询所有。　　　search_str：要查询的字符串。 可以用LIKE里的'%'或‘_’匹配。　　　path：在指定path下查。

mysql> SELECT JSON_SEARCH('{"k1":"v1", "k2":"v2", "k3":"v2"}', 'one', 'v2%');
+----------------------------------------------------------------+
| JSON_SEARCH('{"k1":"v1", "k2":"v2", "k3":"v2"}', 'one', 'v2%') |
+----------------------------------------------------------------+
| "$.k2"                                                         |
+----------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT JSON_SEARCH('{"k1":"v1", "k2":"v2", "k3":"v2"}', 'all', 'v2%');
+----------------------------------------------------------------+
| JSON_SEARCH('{"k1":"v1", "k2":"v2", "k3":"v2"}', 'all', 'v2%') |
+----------------------------------------------------------------+
| ["$.k2", "$.k3"]                                               |
+----------------------------------------------------------------+
1 row in set (0.01 sec)

4. 总结
以需求驱动技术，技术本身没有优略之分，只有业务之分。