MybatisPlus QueryWrapper的null查询

查询字段对应=null的值（特殊）
isNull

QueryWrapperqueryWrapper = newQueryWrapper<>();
queryWrapper
        .isNull("creat_time")
        .ge("count", 12)
        .isNotNull("QQ");
    int result = userMapper.delete(queryWrapper);

between

QueryWrapperqueryWrapper = newQueryWrapper<>();
queryWrapper.between("amount", 20, 30);
    Integer count = userMapper.selectCount(queryWrapper); //返回数据数量