mybatis_plus条件构造器

什么是wapper

Querywrapper中的基本符号的含义与用法

案例

ge:查询user中>=30的数据

@Test
public void testquerywrapper()
{
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.ge("age",30) ;
    List<User> users = userMapper.selectList(wrapper);
    System.out.println(users);
}

eq:查询name="didi"的数据

@Test
public void testquerywrappereq()
{
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("name","didi");
    List<User> users = userMapper.selectList(queryWrapper);
    System.out.println(users);
}

ne:查询name!="didi"的数据

public void testquerywrappereq()
{
    QueryWrapper<User> queryWrapper = new QueryWrapper<>();
    queryWrapper.ne("name","didi");
    List<User> users = userMapper.selectList(queryWrapper);
    System.out.println(users);
}

between:查询age在20到70之间的数据

@Test
public void testqeurywrapperbetween()
{
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.between("age",20,70);
    List<User> users = userMapper.selectList(wrapper);
    System.out.println(users);
}

like:查询名称中包含i的数据

@Test
public void testqeurywrapperlike()
{
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.like("name","i");
    List<User> users = userMapper.selectList(wrapper);
    System.out.println(users);
}

last:查询age再100以内的数据的并排序，取前三条数据

@Test
public void testquerywrapperlast()
{
    QueryWrapper<User> wrapper = new QueryWrapper<>();

    wrapper.lt("age",100).last("limit 3");
    List<User> users = userMapper.selectList(wrapper);
    for (User user:users
         ) {
        System.out.println(user);
    }
}

select：查询所有数据，只要id和name字段

@Test
public void testquerywrapperselect()
{
    QueryWrapper<User> wrapper = new QueryWrapper<>();
    wrapper.select("id","name");
    List<User> users = userMapper.selectList(wrapper);
    for (User user:users
         ) {
        System.out.println(user);
    }
}