详解MyBatis-Plus Wrapper条件构造器查询大全

一、引言

那么那么那么今天来说下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 快速入门案例

二、具体操作

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。

  /**
   * 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 longs = Arrays.asList(1094592041087729666L, 1094590409767661570L);
    List users = userMapper.selectBatchIds(longs);
    users.forEach(System.out::println);
  }

  /**
   * 通过Map参数进行查询
   */
  @Test
  public void selectByMap() {
    Map params = new HashMap<>();
    params.put("name", "张雨琪");
    List users = userMapper.selectByMap(params);
    users.forEach(System.out::println);
  }

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

/**
   * 名字包含雨并且年龄小于40
   * 

   * WHERE name LIKE '%雨%' AND age < 40
   */
  @Test
  public void selectByWrapperOne() {
    QueryWrapper wrapper = new QueryWrapper();
    wrapper.like("name", "雨").lt("age", 40);
    List 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
   * 

   * WHERE name LIKE '%雨%' AND age BETWEEN 20 AND 40 AND email IS NOT NULL
   */
  @Test
  public void selectByWrapperTwo() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
    List 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
   * 

   * WHERE name LIKE '王%' OR age >= 25 ORDER BY age DESC , id ASC
   */
  @Test
  public void selectByWrapperThree() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").or()
        .ge("age", 25).orderByDesc("age").orderByAsc("id");
    List 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
   * 

   * 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 selectByWrapperFour() {
    QueryWrapper 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 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
   * 

   * WHERE name LIKE '王%' AND ( age < 40 OR email IS NOT NULL )
   */
  @Test
  public void selectByWrapperFive() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").and(qw -> qw.lt("age", 40).or().isNotNull("email"));
    List 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
   * 

   * WHERE name LIKE ? OR ( age BETWEEN ? AND ? AND email IS NOT NULL )
   */
  @Test
  public void selectByWrapperSix() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.likeRight("name", "王").or(
        qw -> qw.between("age", 20, 40).isNotNull("email")
    );
    List 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 selectByWrapperSeven() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.nested(qw -> qw.lt("age", 40).or().isNotNull("email"))
        .likeRight("name", "王");
    List users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
  }

  /**
   * 查询年龄为30、31、32
   * WHERE age IN (?,?,?)
   */
  @Test
  public void selectByWrapperEight() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.in("age", Arrays.asList(30, 31, 32));
    List users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
  }

  /**
   * 查询一条数据
   * limit 1
   */
  @Test
  public void selectByWrapperNine() {
    QueryWrapper wrapper = Wrappers.query();
    wrapper.in("age", Arrays.asList(30, 31, 32)).last("limit 1");
    List users = userMapper.selectList(wrapper);
    users.forEach(System.out::println);
  }

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