mysql中json的支持（MySQL中json字段的操作方法）

mysql中json的支持

MySQL中json字段的操作方法

   MySQL5.7.8中引入了json字段，这种类型的字段使用的频率比较低，但是在实际操作中，有些业务仍然在用，我们以此为例，介绍下json字段的操作方法：

还是从例子看起：

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mysql> create table test1(id int,info json); Query OK, 0 rows affected (0.02 sec)   mysql> insert into test1 values (1,'{"name":"yeyz","age":26}'),(2,'{"name":"zhangsan","age":30}'),(3,'{"name":"lisi","age":35}'); Query OK, 3 rows affected (0.02 sec) Records: 3 Duplicates: 0 Warnings: 0   mysql> select * from test1; +------+---------------------------------+ | id  | info              | +------+---------------------------------+ |  1 | {"age": 26, "name": "yeyz"}   | |  2 | {"age": 30, "name": "zhangsan"} | |  3 | {"age": 35, "name": "lisi"}   | +------+---------------------------------+ 3 rows in set (0.00 sec)

    首先我们创建了一个表test1，其中id是int字段，info是json字段，插入了三条数据，如上：

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mysql> select * from test1 where json_extract(info,"$.age")>=30; +------+---------------------------------+ | id  | info              | +------+---------------------------------+ |  2 | {"age": 30, "name": "zhangsan"} | |  3 | {"age": 35, "name": "lisi"}   | +------+---------------------------------+ 2 rows in set (0.00 sec)

   我们可以通过json_extract的方法得到json中的内容。其中：

1、$符号代表的是json的根目录，

2、我们使用$.age相当于取出来了json中的age字段，

3、当然，在函数最前面，应该写上字段名字info

下面来看json中常用的函数：

a、json_valid判断是否是json字段，如果是，返回1，如果不是，返回0

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mysql> select json_valid(2); +---------------+ | json_valid(2) | +---------------+ |       0 | +---------------+ 1 row in set (0.01 sec) mysql> select json_valid('{"num":2}'); +-------------------------+ | json_valid('{"num":2}') | +-------------------------+ |            1 | +-------------------------+ 1 row in set (0.00 sec)   mysql> select json_valid('2'); +-----------------+ | json_valid('2') | +-----------------+ |        1 | +-----------------+ 1 row in set (0.00 sec) mysql> select json_valid('name'); +--------------------+ | json_valid('name') | +--------------------+ |         0 | +--------------------+ 1 row in set (0.00 sec)

   这里需要注意的是，如果传入了字符串2，那么，返回结果是1

b、json_keys传回执行json字段最上一层的key值

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mysql> select json_keys('{"name":"yeyz","score":100}'); +------------------------------------------+ | json_keys('{"name":"yeyz","score":100}') | +------------------------------------------+ | ["name", "score"]            | +------------------------------------------+ 1 row in set (0.01 sec) mysql> select json_keys('{"name":"yeyz","score":{"math":100,"English":95}}'); +----------------------------------------------------------------+ | json_keys('{"name":"yeyz","score":{"math":100,"English":95}}') | +----------------------------------------------------------------+ | ["name", "score"]                       | +----------------------------------------------------------------+ 1 row in set (0.00 sec) #如果有多层，可以在最后面使用$的方法，拿到其中的某一层的目录 mysql> select json_keys('{"name":"yeyz","score":{"math":100,"English":95}}','$.score'); +--------------------------------------------------------------------------+ | json_keys('{"name":"yeyz","score":{"math":100,"English":95}}','$.score') | +--------------------------------------------------------------------------+ | ["math", "English"]                           | +--------------------------------------------------------------------------+ 1 row in set (0.00 sec)

c、json_length函数，返回最上一层的key个数，如果想取到中间的某一层，则可以使用$的方法，如下：

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mysql> select json_length('{"name":"yeyz","score":{"math":100,"English":95},"age":26}'); +---------------------------------------------------------------------------+ | json_length('{"name":"yeyz","score":{"math":100,"English":95},"age":26}') | +---------------------------------------------------------------------------+ |                                     3 | +---------------------------------------------------------------------------+ 1 row in set (0.00 sec)   mysql> select json_length('{"name":"yeyz","score":{"math":100,"English":95},"age":26}','$.score'); +-------------------------------------------------------------------------------------+ | json_length('{"name":"yeyz","score":{"math":100,"English":95},"age":26}','$.score') | +-------------------------------------------------------------------------------------+ |                                          2 | +-------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)

d、json_depth函数，json文件的深度，测试例子如下：

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mysql> select json_depth('{"aaa":1}'),json_depth('{}'); +-------------------------+------------------+ | json_depth('{"aaa":1}') | json_depth('{}') | +-------------------------+------------------+ |            2 |        1 | +-------------------------+------------------+ 1 row in set (0.00 sec)   mysql> select json_depth('{"name":"yeyz","score":{"math":100,"English":95},"age":26}'); +--------------------------------------------------------------------------+ | json_depth('{"name":"yeyz","score":{"math":100,"English":95},"age":26}') | +--------------------------------------------------------------------------+ |                                    3 | +--------------------------------------------------------------------------+ 1 row in set (0.00 sec)

   这里需要注意的是，形如{'aa':1}这种形式的json，其深度是2

e、json_contains_path函数检索json中是否有一个或者多个成员。

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mysql> set @j='{"a":1,"b":2,"c":{"d":4}}'; Query OK, 0 rows affected (0.00 sec) #one的意思是只要包含一个成员，就返回1 mysql> select json_contains_path(@j,'one','$.a','$.e'); +------------------------------------------+ | json_contains_path(@j,'one','$.a','$.e') | +------------------------------------------+ |                    1 | +------------------------------------------+ 1 row in set (0.00 sec) #all的意思是所有的成员都包含，才返回1 mysql> select json_contains_path(@j,'all','$.a','$.e'); +------------------------------------------+ | json_contains_path(@j,'all','$.a','$.e') | +------------------------------------------+ |                    0 | +------------------------------------------+ 1 row in set (0.01 sec)   mysql> select json_contains_path(@j,'one','$.c.d'); +--------------------------------------+ | json_contains_path(@j,'one','$.c.d') | +--------------------------------------+ |                  1 | +--------------------------------------+ 1 row in set (0.00 sec)   mysql> select json_contains_path(@j,'one','$.a.d'); +--------------------------------------+ | json_contains_path(@j,'one','$.a.d') | +--------------------------------------+ |                  0 | +--------------------------------------+ 1 row in set (0.00 sec)

f、json_type函数，判断json中的成员的类型，需要和json_extract结合起来使用。

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mysql> select * from test1; +------+---------------------------------+ | id  | info              | +------+---------------------------------+ |  1 | {"age": 26, "name": "yeyz"}   | |  2 | {"age": 30, "name": "zhangsan"} | |  3 | {"age": 35, "name": "lisi"}   | +------+---------------------------------+ 3 rows in set (0.00 sec) #判断name的类型 mysql> select json_type(json_extract(info,"$.name")) from test1; +----------------------------------------+ | json_type(json_extract(info,"$.name")) | +----------------------------------------+ | STRING                 | | STRING                 | | STRING                 | +----------------------------------------+ 3 rows in set (0.00 sec) #判断age的类型 mysql> select json_type(json_extract(info,"$.age")) from test1; +---------------------------------------+ | json_type(json_extract(info,"$.age")) | +---------------------------------------+ | INTEGER                | | INTEGER                | | INTEGER                | +---------------------------------------+ 3 rows in set (0.00 sec) #判断name和age组合起来的类型，可以看到是array mysql> select json_type(json_extract(info,"$.name","$.age")) from test1; +------------------------------------------------+ | json_type(json_extract(info,"$.name","$.age")) | +------------------------------------------------+ | ARRAY                     | | ARRAY                     | | ARRAY                     | +------------------------------------------------+ 3 rows in set (0.00 sec)

g、*的作用，所有的值,看下面的例子。

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{  "a":1,  "b":2,  "c":    {     "d":4    }  "e":    {    "d":      {      "ddd":      "5"      }    } } mysql> set @j='{"a":1,"b":2,"c":{"d":4},"e":{"d":{"ddd":"5"}}}'; Query OK, 0 rows affected (0.00 sec) #所有成员 mysql> select json_extract(@j,'$.*'); +---------------------------------------+ | json_extract(@j,'$.*')        | +---------------------------------------+ | [1, 2, {"d": 4}, {"d": {"ddd": "5"}}] | +---------------------------------------+ 1 row in set (0.00 sec) #所有成员中的d成员 mysql> select json_extract(@j,'$.*.d'); +--------------------------+ | json_extract(@j,'$.*.d') | +--------------------------+ | [4, {"ddd": "5"}]    | +--------------------------+ 1 row in set (0.00 sec)

以上就是MySQL中json字段的操作方法的详细内容，更多关于MySQL json字段的资料请关注开心学习网其它相关文章！

原文链接：https://cloud.tencent.com/developer/article/1558311