Mybatis-Plus实践学习（二十）

用户1289394

发布于 2023-12-13 16:12:46

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发布于 2023-12-13 16:12:46

文章被收录于专栏：Java学习网

5.4、排序

orderBy

排序：ORDER BY 字段, ...

例: orderBy(true, true, "id", "name") ---> order by id ASC,name ASC

orderByAsc

排序：ORDER BY 字段, ... ASC

例: orderByAsc("id", "name") ---> order by id ASC,name ASC

orderByDesc

排序：ORDER BY 字段, ... DESC

例: orderByDesc("id", "name") ---> order by id DESC,name DESC

测试用例：

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user ORDER BY age DESC
wrapper.orderByDesc("age");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

5.5、逻辑查询

拼接 OR

主动调用 or 表示紧接着下一个方法不是用 and 连接!(不调用 or 则默认为使用 and 连接)

and

AND 嵌套

例: and(i -> i.eq("name", "李白").ne("status", "活着")) ---> and (name = '李白' and status<> '活着')

测试用例：

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user WHERE name = ? OR
age = ?
wrapper.eq("name","李四").or().eq("age", 24);
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

5.6、select

在MP查询中，默认查询所有的字段，如果有需要也可以通过select方法进行指定字段。

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,name,age FROM tb_user WHERE name = ? OR age = ?
wrapper.eq("name", "李四")
.or()
.eq("age", 24)
.select("id", "name", "age");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

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原始发表：2023-12-12，如有侵权请联系 cloudcommunity@tencent.com 删除

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