需求三：这个人的编号是多少

需求："xiaogang 这个人的用户编号是多少？"

从整张表里找出来：

mysql> SELECT * FROM learning_record;
+----+---------+-----------+-------------+----------+------------+
| id | user_id | user_name | path_code   | progress | updated    |
+----+---------+-----------+-------------+----------+------------+
|  1 |     101 | xiaoming  | l1_basic_01 |      100 | 2026-03-01 |
|  2 |     101 | xiaoming  | l1_lang_01  |       60 | 2026-03-04 |
|  3 |     101 | xiaoming  | l1_os_01    |       20 | 2026-03-05 |
|  4 |     102 | xiaohong  | l1_basic_01 |      100 | 2026-03-02 |
|  5 |     102 | xiaohong  | l1_basic_02 |       45 | 2026-03-05 |
|  6 |     103 | xiaogang  | l1_basic_01 |       30 | 2026-03-03 |
|  7 |     104 | zhangsan  | l1_basic_01 |      100 | 2026-03-01 |
|  8 |     104 | zhangsan  | l1_lang_01  |      100 | 2026-03-03 |
|  9 |     104 | zhangsan  | l1_db_01    |       15 | 2026-03-05 |
| 10 |     105 | lisi      | l1_basic_01 |       80 | 2026-03-04 |
+----+---------+-----------+-------------+----------+------------+
mysql>