Mysql json类型

Posted 2020-10-25

mysql json类型

5.7版本支持
原生json类型代替BLOB类型
json数据有效性检查
查询性能提升：不需要遍历所有字符串才能找到数据
支持部分属性索引

1. json格式范例

2. 结构化与非结构化

结构化：二维表结构（行和列） ? 使用SQL语句进行操作
非结构化：使用Key-Value格式定义数据，无结构定义 ? Value可以嵌套Key-Value格式的数据 ? 使用JSON进行实现

SQL创建User表
create table user (
id bigint not null auto_increment,
user_name varchar(10),
age int,
primary key(id) );

JSON定义的User表 ==类似mongodb文档数据库
db.user.insert({ user_name:"tom", age:30 })
db.createCollection("user")

3. json 操作例子

(1)json入门
创建带json字段的表
create table user (
uid int auto_increment,
data json,
primary key(uid));

插入json数据
insert into user values(
null,
‘{"name":"tom",
"age":18,
"address":"sz"
}‘
);

"[email protected]:mysql.sock  [json]>select * from user;
+-----+---------------------------------------------+
| uid | data                                        |
+-----+---------------------------------------------+
|   1 | {"age": 18, "name": "tom", "address": "sz"} |
+-----+---------------------------------------------+
1 row in set (0.01 sec)

insert into user values("age":28,
"mail":"[email protected]"
br/>null,
‘{"name":"jim",
"age":28,
"mail":"[email protected]"
}‘
);

insert into user values ( null, "can you insert it?"); -- 无法插入，因为是JSON类型

4、json常用函数介绍

(1)json_extract
使用json_extract提取数据
原型 : JSON_EXTRACT(json_doc, path[, path] ...)
从list中抽取 下标 为1的元素（下标从0开始）
select json_extract(‘[10, 20, [30, 40]]‘, ‘$[1]‘);

"[email protected]:mysql.sock  [json]>select json_extract(‘[10, 20, [30, 40]]‘, ‘$[1]‘); 
+--------------------------------------------+
| json_extract(‘[10, 20, [30, 40]]‘, ‘$[1]‘) |
+--------------------------------------------+
| 20                                         |
+--------------------------------------------+
1 row in set (0.00 sec)

select json_extract(data, ‘$.name‘),json_extract(data, ‘$.address‘)from user;

"[email protected]:mysql.sock  [json]>select json_extract(data, ‘$.name‘),json_extract(data, ‘$.address‘)from user;
+------------------------------+---------------------------------+
| json_extract(data, ‘$.name‘) | json_extract(data, ‘$.address‘) |
+------------------------------+---------------------------------+
| "tom"                        | "sz"                            |
| "jim"                        | NULL                            |
+------------------------------+---------------------------------+
2 rows in set (0.00 sec)

(2)json_object
将list(K-V对)封装成json格式
原型 : JSON_OBJECT([key, val[, key, val] ...])
select json_object("name", "jery", "email", "[email protected]", "age",33);

"[email protected]:mysql.sock  [json]>select json_object("name", "jery", "email", "[email protected]", "age",33); 
+----------------------------------------------------------------+
| json_object("name", "jery", "email", "[email protected]", "age",33) |
+----------------------------------------------------------------+
| {"age": 33, "name": "jery", "email": "[email protected]"}           |
+----------------------------------------------------------------+
1 row in set (0.00 sec)

insert into user values (
null,
json_object("name", "jery", "email", "[email protected]", "age",33)
);

(3)json_insert
插入数据
原型 : JSON_INSERT(json_doc, path, val[, path, val] ...)

set @j = ‘{ "a": 1, "b": [2, 3]}‘;
select json_insert(@j, ‘$.a‘, 10, ‘$.c‘, ‘[true, false]‘);

"[email protected]:mysql.sock  [json]>select json_insert(@j, ‘$.a‘, 10, ‘$.c‘, ‘[true, false]‘); 
+----------------------------------------------------+
| json_insert(@j, ‘$.a‘, 10, ‘$.c‘, ‘[true, false]‘) |
+----------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": "[true, false]"}        |
+----------------------------------------------------+
1 row in set (0.00 sec)

update user set data = json_insert(data, "$.address_2", "BJ") where uid = 1;
select * from user;

(4)json_merge
合并数据并返回。注意：原数据不受影响
原型 : JSON_MERGE(json_doc, json_doc[, json_doc] ...)
-- 原来有两个JSON
select json_merge(‘{"name": "x"}‘, ‘{"id": 47}‘);

"[email protected]:mysql.sock  [json]>select json_merge(‘{"name": "x"}‘, ‘{"id": 47}‘);
+-------------------------------------------+
| json_merge(‘{"name": "x"}‘, ‘{"id": 47}‘) |
+-------------------------------------------+
| {"id": 47, "name": "x"}                   |
+-------------------------------------------+
1 row in set (0.00 sec)

(5)json_array_append
追加数据 --
原型 : JSON_ARRAY_APPEND(json_doc, path, val[, path, val] ...)
-- json_append 在5.7.9 中重命名为 json_array_append

set @j = ‘["a", ["b", "c"], "d"]‘; -- 下标为1的元素中只有["b", "c"]
select json_array_append(@j, ‘$[1]‘, 1);

"[email protected]:mysql.sock [json]>select json_array_append(@j, ‘$[1]‘, 1);
+----------------------------------+
| json_array_append(@j, ‘$[1]‘, 1) |
+----------------------------------+
| ["a", ["b", "c", 1], "d"] |
+----------------------------------+
1 row in set (0.00 sec)

(6)json_remove
从json记录中删除数据
-- 原型 : JSON_REMOVE(json_doc, path[, path] ...)
set @j = ‘["a", ["b", "c"], "d"]‘;
select json_remove(@j, ‘$[1]‘);
update user set data = json_remove(data, "$.address_2") where uid = 1;

5. json创建索引

JSON 类型数据本身 无法直接 创建索引，
需要将需要索引的JSON数据重新生成虚拟列(Virtual Columns) 之后，对该列进行索引
(1)新建表时创建JSON索引

#抽取data中的name， 生成新的一列，名字为gen_col并将gen_col 作为索引
create table test_inex_1(
data json,
gen_col varchar(10) generated always as (json_extract(data, ‘$.name‘)),
index idx (gen_col)
);

show create table test_inex_1;

"[email protected]:mysql.sock [json]>show create table test_inex_1\G;
1. row
Table: test_inex_1
Create Table: CREATE TABLE test_inex_1 (
data json DEFAULT NULL,
gen_col varchar(10) GENERATED ALWAYS AS (json_extract(data,‘$.name‘)) VIRTUAL,
KEY idx (gen_col)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)

insert into test_inex_1(data) values (‘{"name":"tom", "age":18, "address":"SH"}‘);
insert into test_inex_1(data) values (‘{"name":"jim", "age":28, "address":"SZ"}‘);
select * from test_inex_1;

"[email protected]:mysql.sock  [json]>select * from test_inex_1; 
+---------------------------------------------+---------+
| data                                        | gen_col |
+---------------------------------------------+---------+
| {"age": 18, "name": "tom", "address": "SH"} | "tom"   |
| {"age": 28, "name": "jim", "address": "SZ"} | "jim"   |
+---------------------------------------------+---------+
2 rows in set (0.00 sec)

select json_extract(data,"$.name") as username from test_inex_1 where gen_col=‘"tom"‘; -- 使用‘"tome"‘,用单引号括起来
explain select json_extract(data,"$.name") as username from test_inex_1 where gen_col=‘"tom"‘\G

(2)修改已存在的表创建JSON索引
show create table user;
select from user;
alter table user add user_name varchar(32) generated always as (json_extract(data,"$.name")) virtual;
select user_name from user;
alter table user add index idx(user_name);
select from user where user_name=‘"tom"‘; -- 加单引号
explain select * from user where user_name=‘"tom"‘\G

6. 附录

-- 老师演示JSON的SQL -drop table if exists User;
CREATE TABLE User (
uid BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(32) NOT NULL,
email VARCHAR(256) NOT NULL,
address VARCHAR(512) NOT NULL,
UNIQUE KEY (name),
UNIQUE KEY (email) );
INSERT INTO User VALUES (NULL,‘David‘,‘[email protected]‘,‘Shanghai ...‘); INSERT INTO User VALUES (NULL,‘Amy‘,‘[email protected]‘,‘Beijing ...‘);
INSERT INTO User VALUES (NULL,‘Tom‘,‘[email protected]‘,‘Guangzhou ...‘);
SELECT * FROM User;
ALTER TABLE User ADD COLUMN address2 VARCHAR(512) NOT NULL; ALTER TABLE User ADD COLUMN passport VARCHAR(64) NOT NULL;

DROP TABLE IF EXISTS UserJson;
CREATE TABLE UserJson(
uid BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
data JSON );
truncate table UserJson;
insert into UserJson SELECT uid,JSON_OBJECT(‘name‘,name,‘email‘,email,‘address‘,address) AS data FROM User;
SELECT * FROM UserJson;
SELECT uid,JSON_EXTRACT(data,‘$.address2‘) from UserJson;
UPDATE UserJson set data = json_insert(data,"$.address2","HangZhou ...") where uid = 1;
SELECT JSON_EXTRACT(data,‘$.address[1]‘) from UserJson;
select json_merge(JSON_EXTRACT(data,‘$.address‘) ,JSON_EXTRACT(data,‘$.address2‘)) from UserJson;

begin;
UPDATE UserJson set data = json_array_append(data,"$.address",JSON_EXTRACT(data,‘$.address2‘)) where JSON_EXTRACT(data,‘$.address2‘) IS NOT NULL AND uid >0;
select JSON_EXTRACT(data,‘$.address‘) from UserJson;
UPDATE UserJson set data = JSON_REMOVE(data,‘$.address2‘) where uid>0;
commit;

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