代码下载:https://github.com/Jackson0714/study-mybatis-plus.git
mybatis-plus的查询功能非常强大, 上一篇,我们通过例题的方式讲解了mybatis-plus的高级查询功能:条件查询,这一篇我们继续以例题的方式讲解mybatis-plus的高级查询功能。
准备数据
1 DROP TABLE IF EXISTS user;
2
3 CREATE TABLE user (user
4 id BIGINT(20) PRIMARY KEY NOT NULL COMMENT '主键',
5 name VARCHAR(30) DEFAULT NULL COMMENT '姓名',
6 age INT(11) DEFAULT NULL COMMENT '年龄',
7 email VARCHAR(50) DEFAULT NULL COMMENT '邮箱',
8 manager_id BIGINT(20) DEFAULT NULL COMMENT '直属上级id',
9 create_time DATETIME DEFAULT NULL COMMENT '创建时间',
10 CONSTRAINT manager_fk FOREIGN KEY (manager_id)
11 REFERENCES user (id)
12 ) ENGINE=INNODB CHARSET=UTF8;
13
14 DELETE FROM user;
15
16 INSERT INTO user (id, name, age, email,manager_id,create_time) VALUES
17 (1, 'Jone', 18, 'test1@baomidou.com', null, '2020-01-01 14:20:20'),
18 (2, 'Jack', 20, 'test2@baomidou.com', 1, '2020-01-20 14:20:20'),
19 (3, 'Tom', 28, 'test3@baomidou.com', 2, '2020-01-15 14:20:20'),
20 (4, 'Sandy', 21, 'test4@baomidou.com', 2, '2020-01-12 14:20:20'),
21 (5, 'Billie', 24, 'test5@baomidou.com', 2, '2020-01-22 14:20:20');
User
表结构如下:
id | name | age | manager_id | create_time | ||
---|---|---|---|---|---|---|
1 | Jone | 18 | test1@baomidou.com | null | 2020-01-01 14:20:20 | 2020-01-01 14:20:20 |
2020-01-01 14:20:20 | ||||||
2 | Jack | 20 | test2@baomidou.com | 1 | 2020-01-20 14:20:20 | 2020-01-20 14:20:20 |
2020-01-20 14:20:20 | ||||||
3 | Tom | 28 | test3@baomidou.com | 2 | 2020-01-15 14:20:20 | 2020-01-15 14:20:20 |
2020-01-15 14:20:20 | ||||||
4 | Sandy | 21 | test4@baomidou.com | 2 | 2020-01-12 14:20:20 | 2020-01-12 14:20:20 |
2020-01-12 14:20:20 | ||||||
5 | Billie | 24 | test5@baomidou.com | 2 | 2020-01-22 14:20:20 | 2020-01-22 14:20:20 |
2020-01-22 14:20:20 |
难度系数 ★★★★
难度系数 ★★★★
考察 apply 和 inSql的用法
这里需要用到子查询,先查询出name为“J”开头的集合1,然后再查询出manger_id 与集合1中的id相等的集合
SELECT * FROM demo.user
WHERE date_format(create_time, '%Y-%m-%d') ='2020-01-15'
AND manager_id in (SELECT id FROM demo.user WHERE name LIKE 'J%');
1 SELECT user1.* FROM demo.user AS user1
2 INNER JOIN demo.user AS user2 ON user1.manager_id = user2.id
3 WHERE date_format(user1.create_time, '%Y-%m-%d') ='2020-01-15'
4 AND user2.name LIKE 'J%'
apply有两种用法:
apply(String applySql, Object... params)
apply(boolean condition, String applySql, Object... params)
第一种有SQL注入的风险,稍后我们再介绍,先介绍第二种用法
queryWrapper.apply("date_format(create_time, '%Y-%m-%d')={0}","2020-01-15")
1 inSql
2 inSql(R column, String inValue)
3 inSql(boolean condition, R column, String inValue)
4 字段 IN ( sql语句 )
5 例: inSql("age", "1,2,3,4,5,6")--->age in (1,2,3,4,5,6)
6 例: inSql("id", "select id from table where id < 3")--->id in (select id from table where id < 3)
例题中的写法:
.inSql("manager_id", "select id from user where name like 'J%'");
1 /*
2 * 描述:例1.4 查询创建日期为2020年1月15日并且直属上级的名字为“J”开头的
3 * SQL语句方案一:SELECT * FROM demo.user where date_format(create_time, '%Y-%m-%d') ='2020-01-15' AND manager_id in (select id from user where name like 'J%');
4 * SQL语句方案二:SELECT user1.* FROM demo.user AS user1 INNER JOIN demo.user AS user2 ON user1.manager_id = user2.id WHERE date_format(user1.create_time, '%Y-%m-%d') ='2020-01-15' AND user2.name LIKE 'J%'
5 * 作者:博客园-悟空聊架构
6 * 时间:2019-01-29
7 * Github:https://github.com/Jackson0714/study-mybatis-plus.git
8 * 博客园:https://www.cnblogs.com/jackson0714
9 * */
10 @Test
11 public void testSelectByQueryWrapper4() {
12 System.out.println(("----- 查询创建日期为2020年1月15日并且直属上级的名字为“J”开头的 ------"));
13 QueryWrapper<User> queryWrapper = new QueryWrapper<>();
14 //queryWrapper.apply("date_format(create_time, '%Y-%m-%d')='2020-01-15' or true or true") // SQL注入
15 queryWrapper.apply("date_format(create_time, '%Y-%m-%d')={0}","2020-01-15")
16 .inSql("manager_id", "select id from user where name like 'J%'");
17 List<User> userList = userMapper.selectList(queryWrapper);
18 userList.forEach(System.out::println);
19 }
查询日志:
SQL语句执行结果
apply的第一种写法,传入的参数是 '2020-01-15'
queryWrapper.apply("date_format(create_time, '%Y-%m-%d')='2020-01-15'")
如果传入的是 "'2020-01-15' or true or true",则apply写法如下:
queryWrapper.apply("date_format(create_time, '%Y-%m-%d')='2020-01-15' or true or true")
则拼接后的SQL语句如下:
SELECT id,name,age,email,manager_id,create_time FROM user
WHERE (date_format(create_time, '%Y-%m-%d')='2020-01-15' or true or true AND manager_id IN (select id from user where name like 'J%'))
执行该SQL语句,可以查询出所有user数据,造成隐私泄露。
悟空聊架构
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