MyBatis-Plus Advanced Query Cases and Detailed Explanations

The article introduces advanced query capabilities of MyBatis-Plus, following a brief overview of environment setup and basic queries.

A sample User table is defined with columns id, name, age, and email.

Case 1: Find users whose name contains "Ja" and age is less than 30

SQL condition:

name LIKE '%Ja%' AND age < 30

/*
 * Description: Example 1.1 – Query users with name containing "Ja" and age < 30
 */
@Test
public void testSelectByQueryWrapper() {
    System.out.println("----- Query users with name containing \"Ja\" and age < 30 -----");
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.like("name", "ja").lt("age", 30);
    List<User> userList = userMapper.selectList(queryWrapper);
    userList.forEach(System.out::println);
}

Case 2: Find users whose name contains "a", age between 15 and 25, and email is not null

SQL condition:

name LIKE '%a%' AND age BETWEEN 15 AND 25 AND email IS NOT NULL

/*
 * Description: Example 1.2 – Query users with name containing "a", age 15‑25, email not null
 */
@Test
public void testSelectByQueryWrapper2() {
    System.out.println("----- Query users with name containing \"a\", age 15‑25, email not null -----");
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.like("name", "a").between("age", 15, 25).isNotNull("email");
    List<User> userList = userMapper.selectList(queryWrapper);
    userList.forEach(System.out::println);
}

Case 3: Find users whose name starts with "J", age ≥ 25, ordered by age descending then id ascending

SQL condition:

name LIKE 'J%' AND age >= 25 ORDER BY age DESC, id ASC

/*
 * Description: Example 1.3 – Query users with name starting with "J", age ≥ 25, ordered by age desc, id asc
 */
@Test
public void testSelectByQueryWrapper3() {
    System.out.println("----- Query users with name starting with \"J\", age ≥ 25, ordered -----");
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.likeRight("name", "J").or().gt("age", 26)
                .orderByDesc("age").orderByAsc("id");
    List<User> userList = userMapper.selectList(queryWrapper);
    userList.forEach(System.out::println);
}

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