JAVA分享篇（35）基础知识大总结

比如说在上面的场景中我还要加上一个年龄大于18的条件

LambdaQueryWrapper的写法就是

LambdaQueryWrapper<User> lqw = new LambdaQueryWrapper<User>();
lqw.eq(User::getUserName,"小陈");
lqw.gt(User::getAget,18);
List<User> list = UserMapper.selectList(lqw);

而LambdaQueryChainWrapper 的写法就是

List<User> list = new LambdaQueryChainWrapper<>(UserMapper)
        .eq(User::getUserName,"小陈")
      .gt(User::getAget,18)
        .list();

聚合排序类

groupBy 分组( orderByAsc ，orderByDesc  ，orderBy排序同理)

groupBy(R... columns)
groupBy(boolean condition, R... columns)

QueryWrapper写法：

QueryWrapper<User> qw = new QueryWrapper<User>();
qw.like("user_name","王");
qw.groupBy("age","type");
List<User> list = UserMapper.selectList(qw); <