标签:no json 特性 JSON MySQL8.0 details address emp
要在MySQL
中存储数据,就必须定义数据库和表结构(schema
),这是一个主要的限制。为了应对这一点,从MySQL 5.7
开始,MySQL
支恃了JavaScript
对象表示(JavaScriptObject Notation,JSON
)数据类型。之前,这类数据不是单独的数据类型,会被存储为字符串。新的JSON
数据类型提供了自动验证的JSON
文档以及优化的存储格式。
JSON
文档以二进制格式存储,它提供以下功能:
- 对文档元素的快速读取访问。
- 当服务器再次读取
JSON
文档时,不需要重新解析文本获取该值。 - 通过键或数组索引直接查找子对象或嵌套值,而不需要读取文档中的所有值。
一、创建数据
1.1 创建测试表
mysql> create table employees.emp_details (
-> emp_no int primary key,
-> details json
-> );
Query OK, 0 rows affected (0.17 sec)
mysql> desc employees.emp_details;
+---------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+-------+
| emp_no | int(11) | NO | PRI | NULL | |
| details | json | YES | | NULL | |
+---------+---------+------+-----+---------+-------+
2 rows in set (0.00 sec)
1.2 插入JSON
mysql> insert into employees.emp_details (emp_no, details)
-> values ('1',
-> '{"location":"IN","phone":"+11800000000","email":"abc@example.com","address":{"line1":"abc","line2":"xyz street","city":"Bangalore","pin":"560103"}}'
-> );
Query OK, 1 row affected (0.13 sec)
mysql> select emp_no, details from employees.emp_details;
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| emp_no | details |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | {"email": "abc@example.com", "phone": "+11800000000", "address": {"pin": "560103", "city": "Bangalore", "line1": "abc", "line2": "xyz street"}, "location": "IN"} |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
1.3 检索JSON
可以使用->
和->>
运算符检索JSON
列的字段:
mysql> select emp_no, details -> '$.address.pin' pin
-> from employees.emp_details;
+--------+----------+
| emp_no | pin |
+--------+----------+
| 1 | "560103" |
+--------+----------+
1 row in set (0.00 sec)
如果不用引号检索数据,可以使用->>
运算符(推荐此方式)
mysql> select emp_no, details ->> '$.address.pin' pin
-> from employees.emp_details;
+--------+--------+
| emp_no | pin |
+--------+--------+
| 1 | 560103 |
+--------+--------+
1 row in set (0.00 sec)
二、JSON函数
MySQL
提供了许多处理JSON
数据的函数,让我们看看最常用的几种函数。
2.1 优雅浏览
想要以优雅的格式显示JSON
值,请使用JSON_PRETTY()
函数
mysql> select emp_no, json_pretty(details)
-> from employees.emp_details\G
*************************** 1. row ***************************
emp_no: 1
json_pretty(details): {
"email": "abc@example.com",
"phone": "+11800000000",
"address": {
"pin": "560103",
"city": "Bangalore",
"line1": "abc",
"line2": "xyz street"
},
"location": "IN"
}
1 row in set (0.00 sec)
2.2 查找
可以在WHERE
子句中使用col ->> path
运算符来引用JSON
的某一列
mysql> select emp_no, details
-> from employees.emp_details
-> where details ->> '$.address.pin' = "560103";
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| emp_no | details |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | {"email": "abc@example.com", "phone": "+11800000000", "address": {"pin": "560103", "city": "Bangalore", "line1": "abc", "line2": "xyz street"}, "location": "IN"} |
+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
也可以使用JSON_CONTAINS
函数查询数据。如果找到了数据,则返回1,否则返回0
mysql> select json_contains(details ->> '$.address.pin',"560103")
-> from employees.emp_details;
+-----------------------------------------------------+
| json_contains(details ->> '$.address.pin',"560103") |
+-----------------------------------------------------+
| 1 |
+-----------------------------------------------------+
1 row in set (0.00 sec)
如何查询一个key
?使用JSON_CONTAINS_PATH
函数检查address.line1
是否存在
mysql> select json_contains_path(details, 'one', "$.address.line1")
-> from employees.emp_details;
+-------------------------------------------------------+
| json_contains_path(details, 'one', "$.address.line1") |
+-------------------------------------------------------+
| 1 |
+-------------------------------------------------------+
1 row in set (0.00 sec)
one
表示至少应该存在一个键,检查address.line1
或者address.line2
是否存在
mysql> select json_contains_path(details, 'one', "$.address.line1", "$.address.line2")
-> from employees.emp_details;
+--------------------------------------------------------------------------+
| json_contains_path(details, 'one', "$.address.line1", "$.address.line2") |
+--------------------------------------------------------------------------+
| 1 |
+--------------------------------------------------------------------------+
1 row in set (0.00 sec)
如果要检查address.line1
或者address.line5
是否同时存在,可以使用all
,而不是one
mysql> select json_contains_path(details, 'all', "$.address.line1", "$.address.line5")
-> from employees.emp_details;
+--------------------------------------------------------------------------+
| json_contains_path(details, 'all', "$.address.line1", "$.address.line5") |
+--------------------------------------------------------------------------+
| 0 |
+--------------------------------------------------------------------------+
1 row in set (0.00 sec)
2.3 修改
可以使用三种不同的函数来修改数据:JSON_SET()
、JSON_INSERT()
和JSON_REPLACE()
。在MySQL 8
之前的版本中,我们还需要对整个列进行完整的更新,这并不是最佳的方法。
2.3.1 JSON_SET()
替换现有值并添加不存在的值
mysql> update employees.emp_details
-> set details = json_set(details, "$.address.pin", "560100", "$.nickname","kai")
-> where emp_no = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select emp_no, json_pretty(details)
-> from employees.emp_details\G
*************************** 1. row ***************************
emp_no: 1
json_pretty(details): {
"email": "abc@example.com",
"phone": "+11800000000",
"address": {
"pin": "560100",
"city": "Bangalore",
"line1": "abc",
"line2": "xyz street"
},
"location": "IN",
"nickname": "kai"
}
1 row in set (0.00 sec)
2.3.2 JSON_INSERT()
插入值,但不替换现有值
在这种情况下,$.address.pin
不会被更新,只会添加一个新的字段$.address.line4
mysql> update employees.emp_details
-> set details = json_insert(details, "$.address.pin", "560132", "$.address.line4","A Wing")
-> where emp_no = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select emp_no, json_pretty(details)
-> from employees.emp_details\G
*************************** 1. row ***************************
emp_no: 1
json_pretty(details): {
"email": "abc@example.com",
"phone": "+11800000000",
"address": {
"pin": "560100",
"city": "Bangalore",
"line1": "abc",
"line2": "xyz street",
"line4": "A Wing"
},
"location": "IN",
"nickname": "kai"
}
1 row in set (0.01 sec)
2.3.3 JSON_REPLACE()
仅替换现有值
在这种情况下,$.address.line5
不会被添加,只有$.address.pin
会被更新
mysql> update employees.emp_details
-> set details = json_replace(details, "$.address.pin", "560132", "$.address.line5","Landmark")
-> where emp_no = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select emp_no, json_pretty(details)
-> from employees.emp_details\G
*************************** 1. row ***************************
emp_no: 1
json_pretty(details): {
"email": "abc@example.com",
"phone": "+11800000000",
"address": {
"pin": "560132",
"city": "Bangalore",
"line1": "abc",
"line2": "xyz street",
"line4": "A Wing"
},
"location": "IN",
"nickname": "kai"
}
1 row in set (0.00 sec)
2.4 删除
JSON_REMOVE
能从JSON
文档中删除数据
mysql> update employees.emp_details
-> set details = json_remove(details, "$.address.line4")
-> where emp_no = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select emp_no, json_pretty(details)
-> from employees.emp_details\G
*************************** 1. row ***************************
emp_no: 1
json_pretty(details): {
"email": "abc@example.com",
"phone": "+11800000000",
"address": {
"pin": "560132",
"city": "Bangalore",
"line1": "abc",
"line2": "xyz street"
},
"location": "IN",
"nickname": "kai"
}
1 row in set (0.00 sec)
2.5 其他函数
JSON_KEYS()
:获取JSON
文档中的所有键
mysql> select json_keys(details),json_keys(details ->> "$.address")
-> from employees.emp_details
-> where emp_no= 1;
+-------------------------------------------------------+------------------------------------+
| json_keys(details) | json_keys(details ->> "$.address") |
+-------------------------------------------------------+------------------------------------+
| ["email", "phone", "address", "location", "nickname"] | ["pin", "city", "line1", "line2"] |
+-------------------------------------------------------+------------------------------------+
1 row in set (0.00 sec)
JSON_LENGTH()
:给出JSON
文档中的元素数
mysql> select json_length(details), json_length(details ->> "$.address")
-> from employees.emp_details
-> where emp_no= 1;
+----------------------+--------------------------------------+
| json_length(details) | json_length(details ->> "$.address") |
+----------------------+--------------------------------------+
| 5 | 4 |
+----------------------+--------------------------------------+
1 row in set (0.00 sec)
延伸阅读: https://dev.mysql.com/doc/refman/8.0/en/json-function-reference.html
参考文章
标签:no,json,特性,JSON,MySQL8.0,details,address,emp 来源: https://www.cnblogs.com/ciel717/p/16190694.html
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