MySQL内置了一系列JSON函数,JSON函数是对数据库中JSON类型的数据进行处理的函数。
目录
MySQL JSON函数
准备数据
首先,在名称为test的数据库中创建数据表test_json。
创建数据表
数据表创建语句如下:
mysql> use test;
Database changed
mysql> CREATE TABLE test_json (
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
content JSON
);
Query OK, 0 rows affected
mysql> desc test_json;
+---------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| content | json | YES | | NULL | |
+---------+---------+------+-----+---------+----------------+
2 rows in set
新增数据
接下来,向test_json数据表中插入演示数据。
INSERT INTO test_json (content) VALUES('{"name":"zhangsan", "age":20, "address":{"province":
"beijing", "city":"haidian"}}');
查询JSON指定内容
可以使用“->”和“->>”查询JSON数据中指定的内容。
示例如下:
mysql> SELECT content->'$.name' FROM test_json WHERE id = 1;
+-------------------+
| content->'$.name' |
+-------------------+
| "zhangsan" |
+-------------------+
1 row in set (0.00 sec)
mysql> SELECT content->>'$.address.province' FROM test_json WHERE id = 1;
+--------------------------------+
| content->>'$.address.province' |
+--------------------------------+
| beijing |
+--------------------------------+
1 row in set (0.00 sec)
JSON_CONTAINS
JSON_CONTAINS(json_doc,value)函数 查询JSON类型的字段中是否包含value数据。如果包含则返回1,否则返回0。其中,json_doc为JSON类型的数据,value为要查找的数据。
使用示例如下:
mysql> SELECT JSON_CONTAINS(content, '{"name":"zhangsan"}') FROM test_json WHERE id = 1;
+-----------------------------------------------+
| JSON_CONTAINS(content, '{"name":"zhangsan"}') |
+-----------------------------------------------+
| 1 |
+-----------------------------------------------+
注意:value必须是一个JSON字符串。
JSON_SEARCH
JSON_SEARCH(json_doc ->> '$[*].key',type,value)函数在JSON类型的字段指定的key中,查找字符串value。如果找到value值,则返回索引数据。
使用示例如下:
mysql> SELECT JSON_SEARCH(content ->> '$.address', 'one', 'haidian') FROM test_json WHERE id = 1;
+--------------------------------------------------------+
| JSON_SEARCH(content ->> '$.address', 'one', 'haidian') |
+--------------------------------------------------------+
| "$.city" |
+--------------------------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT JSON_SEARCH(content ->> '$.address', 'all', 'beijing') FROM test_json WHERE id = 1;
+--------------------------------------------------------+
| JSON_SEARCH(content ->> '$.address', 'all', 'beijing') |
+--------------------------------------------------------+
| "$.province" |
+--------------------------------------------------------+
1 row in set (0.00 sec)
注意:函数的第二个参数type,取值可以是one或者all。当取值为one时,如果找到value值,则返回value值的第一个索引数据;当取值为all时,如果找到value值,则返回value值的所有索引数据。
JSON_PRETTY
JSON_PRETTY(json_doc)函数以优雅的格式显示JSON数据。
使用示例如下:
mysql> SELECT JSON_PRETTY(content) FROM test_json WHERE id = 1;
+------------------------------------------------------------------------------------------------------------+
| JSON_PRETTY(content) |
+------------------------------------------------------------------------------------------------------------+
| {
"age": 20,
"name": "zhangsan",
"address": {
"city": "haidian",
"province": "beijing"
}
} |
+------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
JSON_DEPTH
JSON_DEPTH(json_doc)函数返回JSON数据的最大深度。
使用示例如下:
mysql> SELECT JSON_DEPTH(content) FROM test_json WHERE id = 1;
+---------------------+
| JSON_DEPTH(content) |
+---------------------+
| 3 |
+---------------------+
1 row in set (0.00 sec)
JSON_LENGTH
JSON_LENGTH(json_doc[,path])函数返回JSON数据的长度。
使用示例如下:
mysql> SELECT JSON_LENGTH(content) FROM test_json WHERE id = 1;
+----------------------+
| JSON_LENGTH(content) |
+----------------------+
| 3 |
+----------------------+
1 row in set (0.00 sec)
JSON_KEYS
JSON_KEYS(json_doc[,path])函数返回JSON数据中顶层key组成的JSON数组。
使用示例如下:
mysql> SELECT JSON_KEYS(content) FROM test_json WHERE id = 1;
+----------------------------+
| JSON_KEYS(content) |
+----------------------------+
| ["age", "name", "address"] |
+----------------------------+
1 row in set (0.00 sec)
JSON_INSERT
JSON_INSERT(json_doc,path,val[,path,val] ...)函数用于向JSON数据中插入数据。
使用示例如下:
mysql> SELECT JSON_INSERT(content, '$.address.zip_code','10000') FROM test_json WHERE id = 1;
+-------------------------------------------------------------------------------------------------------------+
| JSON_INSERT(content, '$.address.zip_code','10000') |
+-------------------------------------------------------------------------------------------------------------+
| {"age": 20, "name": "zhangsan", "address": {"city": "haidian", "province": "beijing", "zip_code": "10000"}} |
+-------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
接下来,查看test_json表中的数据。
mysql> SELECT JSON_PRETTY(content) FROM test_json WHERE id = 1;
+------------------------------------------------------------------------------------------------------------+
| JSON_PRETTY(content) |
+------------------------------------------------------------------------------------------------------------+
| {
"age": 20,
"name": "zhangsan",
"address": {
"city": "haidian",
"province": "beijing"
}
} |
+------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
可以看到,JSON_INSERT()函数并没有更新数据表中的数据,只是修改了显示结果。
JSON_REMOVE
JSON_REMOVE(json_doc,path[,path] ...)函数用于移除JSON数据中指定key的数据。
使用示例如下:
mysql> SELECT JSON_REMOVE(content, '$.address.city') FROM test_json WHERE id = 1;
+---------------------------------------------------------------------+
| JSON_REMOVE(content, '$.address.city') |
+---------------------------------------------------------------------+
| {"age": 20, "name": "zhangsan", "address": {"province": "beijing"}} |
+---------------------------------------------------------------------+
1 row in set (0.02 sec)
接下来,查看test_json表中的数据。
mysql> SELECT JSON_PRETTY(content) FROM test_json WHERE id = 1;
+-----------------------------------------------------------------------------------------------------+
| JSON_PRETTY(content) |
+-----------------------------------------------------------------------------------------------------+
| {
"age": 20,
"name": "zhangsan",
"address": {
"city": "haidian",
"province": "beijing"
}
} |
+-----------------------------------------------------------------------------------------------------+
1 row in set (0.02 sec)
JSON_REPLACE
JSON_REPLACE(json_doc,path,val[,path,val] ...)函数用于更新JSON数据中指定Key的数据。
使用示例如下:
mysql> SELECT JSON_REPLACE(content,'$.age',22) FROM test_json WHERE id = 1;
+----------------------------------------------------------------------------------------+
| JSON_REPLACE(content,'$.age',22) |
+----------------------------------------------------------------------------------------+
| {"age": 22, "name": "zhangsan", "address": {"city": "haidian", "province": "beijing"}} |
+----------------------------------------------------------------------------------------+
1 row in set (0.02 sec)
接下来,查看test_json表中的数据。
mysql> SELECT JSON_PRETTY(content) FROM test_json WHERE id = 1;
+-----------------------------------------------------------------------------------------------------+
| JSON_PRETTY(content) |
+-----------------------------------------------------------------------------------------------------+
| {
"age": 20,
"name": "zhangsan",
"address": {
"city": "haidian",
"province": "beijing"
}
} |
+-----------------------------------------------------------------------------------------------------+
1 row in set (0.02 sec)
可以看到,JSON_REPLACE()函数并没有更新数据表中的数据,只是修改了显示结果。
JSON_SET
JSON_SET(json_doc,path,val[,path,val] ...)函数用于向JSON数据中插入数据。
使用示例如下:
mysql> SELECT JSON_SET(content, '$.address.street', '北清街道' ) FROM test_json WHERE id = 1;
+--------------------------------------------------------------------------------------------------------------+
| JSON_SET(content, '$.address.street', '北清街道' ) |
+--------------------------------------------------------------------------------------------------------------+
| {"age": 20, "name": "zhangsan", "address": {"city": "haidian", "street": "北清街道", "province": "beijing"}} |
+--------------------------------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
接下来,查看test_json表中的数据。
mysql> SELECT JSON_PRETTY(content) FROM test_json WHERE id = 1;
+-----------------------------------------------------------------------------------------------------+
| JSON_PRETTY(content) |
+-----------------------------------------------------------------------------------------------------+
| {
"age": 20,
"name": "zhangsan",
"address": {
"city": "haidian",
"province": "beijing"
}
} |
+-----------------------------------------------------------------------------------------------------+
1 row in set (0.03 sec)
JSON_TYPE
JSON_TYPE(json_val)函数用于返回JSON数据的JSON类型,MySQL中支持的JSON类型除了可以是MySQL中的数据类型外,还可以是OBJECT和ARRAY类型,其中OBJECT表示JSON对象,ARRAY表示JSON数组。
使用示例如下:
mysql> SELECT JSON_TYPE(content) FROM test_json WHERE id = 1;
+--------------------+
| JSON_TYPE(content) |
+--------------------+
| OBJECT |
+--------------------+
1 row in set (0.03 sec)
JSON_VALID
JSON_VALID(value)函数用于判断value的值是否是有效的JSON数据,
如果是,则返回1,否则返回0,如果value的值为NULL,则返回NULL。
使用示例如下:
mysql> SELECT JSON_VALID('{"name":"zhangsan"}'), JSON_VALID('name'), JSON_VALID(NULL);
+-----------------------------------+--------------------+------------------+
| JSON_VALID('{"name":"zhangsan"}') | JSON_VALID('name') | JSON_VALID(NULL) |
+-----------------------------------+--------------------+------------------+
| 1 | 0 | NULL |
+-----------------------------------+--------------------+------------------+
1 row in set (0.03 sec)
注意:了解更多关于JSON函数的知识可以查看官网https://dev.mysql.com/doc/refman/8.0/en/json-function-reference.html
总结
本文简单介绍了MySQL中常用的JSON函数,以示例的形式介绍每种JSON函数的作用和用法。
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