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革命尚未成功,同志仍须努力下载JDK17

作者:Albert.Wen  添加时间:2022-05-04 17:16:03  修改时间:2024-12-12 03:29:05  分类:06.Java框架/系统  编辑

一、引言

今天来说下MP中强大的条件查询功能。

本章是基于上个案例来讲的:MyBaits-Plus 快速入门示例

二、具体操作

1、首先来说说基本的查询吧,根据主键或者简单的查询条件进行查询。

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/**
 * 通过单个ID主键进行查询
 */
@Test
public void selectById() {
    User user = userMapper.selectById(1094592041087729666L);
    System.out.println(user);
}
 
/**
 * 通过多个ID主键查询
 */
@Test
public void selectByList() {
    List<Long> longs = Arrays.asList(1094592041087729666L, 1094590409767661570L);
    List<User> users = userMapper.selectBatchIds(longs);
    users.forEach(System.out::println);
}
 
/**
 * 通过Map参数进行查询
 */
@Test
public void selectByMap() {
    Map<String, Object> params = new HashMap<>();
    params.put("name", "张雨琪");
    List<User> users = userMapper.selectByMap(params);
    users.forEach(System.out::println);
}

2、MyBatis-Plus还提供了Wrapper条件构造器,具体使用看如下代码:

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/**
 * 名字包含雨并且年龄小于40
 * <p>
 * WHERE name LIKE '%雨%' AND age < 40
 */
@Test
public void selectByWrapper1() {
    QueryWrapper<User> wrapper = new QueryWrapper();
    wrapper.like("name", "雨").lt("age", 40);
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 名字包含雨
 * 年龄大于20小于40
 * 邮箱不能为空
 * <p>
 * WHERE name LIKE '%雨%' AND age BETWEEN 20 AND 40 AND email IS NOT NULL
 */
@Test
public void selectByWrapper2() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 名字为王性
 * 或者年龄大于等于25
 * 按照年龄降序排序,年龄相同按照id升序排序
 * <p>
 * WHERE name LIKE '王%' OR age >= 25 ORDER BY age DESC , id ASC
 */
@Test
public void selectByWrapper3() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").or()
            .ge("age", 25).orderByDesc("age").orderByAsc("id");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 查询创建时间为2019年2月14
 * 并且上级领导姓王
 * <p>
 * WHERE date_format(create_time,'%Y-%m-%d') = '2019-02-14' AND manager_id IN (select id from user where name like '王%')
 */
@Test
public void selectByWrapper4() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.apply("date_format(create_time,'%Y-%m-%d') = {0}", "2019-02-14")
            .inSql("manager_id", "select id from user where name like '王%'");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 查询王姓
 * 并且年龄小于40或者邮箱不为空
 * <p>
 * WHERE name LIKE '王%' AND ( age < 40 OR email IS NOT NULL )
 */
@Test
public void selectByWrapper5() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").and(qw -> qw.lt("age", 40).or().isNotNull("email"));
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 查询王姓
 * 并且年龄大于20 、年龄小于40、邮箱不能为空
 * <p>
 * WHERE name LIKE ? OR ( age BETWEEN ? AND ? AND email IS NOT NULL )
 */
@Test
public void selectByWrapper6() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").or(
            qw -> qw.between("age", 20, 40).isNotNull("email")
    );
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * (年龄小于40或者邮箱不为空) 并且名字姓王
 * WHERE ( age < 40 OR email IS NOT NULL ) AND name LIKE '王%'
 */
@Test
public void selectByWrapper7() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.nested(qw -> qw.lt("age", 40).or().isNotNull("email"))
            .likeRight("name", "王");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 查询年龄为30、31、32
 * WHERE age IN (?,?,?)
 */
@Test
public void selectByWrapper8() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.in("age", Arrays.asList(30, 31, 32));
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}
 
/**
 * 查询一条数据
 * limit 1
 */
@Test
public void selectByWrapper9() {
    QueryWrapper<User> wrapper = Wrappers.query();
    wrapper.in("age", Arrays.asList(30, 31, 32)).last("limit 1");
    List<User> users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
}

工作中的一个示例:

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@Test
void test_01() {
    List<EmailTask> emailTaskList = this.emailTaskService
        .list(Wrappers.<EmailTask>lambdaQuery()
            .or(qw -> qw
                .eq(EmailTask::getMakeQueueStatus, 1)
                .eq(EmailTask::getStartType, 2)
                .lt(EmailTask::getStartTime, LocalDateTime.now())
            )
            .or(qw -> qw
                .eq(EmailTask::getMakeQueueStatus, 1)
                .eq(EmailTask::getStartType, 3)
            )
        );
    System.out.println(emailTaskList);
}

输出:

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SELECT
    id,user_id,name,template_ids,receiver_ids,add_time,update_time 
FROM email_task   
    WHERE
(
    (make_queue_status = 1 AND start_type = 2 AND start_time < '2022-07-15T17:00:37.320896400')
    OR
    (make_queue_status = 1 AND start_type = 3)
)

 

 

 

摘自:https://jiannan.blog.csdn.net/article/details/91447509