需求二：谁还差得远

需求："哪些记录的进度还不到一半？要人名、路线和进度。"

查询结果有几行？

mysql> SELECT user_name, path_code, progress FROM learning_record WHERE progress < 50;
+-----------+-------------+----------+
| user_name | path_code   | progress |
+-----------+-------------+----------+
| xiaoming  | l1_os_01    |       20 |
| xiaohong  | l1_basic_02 |       45 |
| xiaogang  | l1_basic_01 |       30 |
| zhangsan  | l1_db_01    |       15 |
+-----------+-------------+----------+
mysql>