如何在 MySQL 中将逗号分隔的列表设置为表？

Mysql> select 10 Number UNION ALL select 20 Number UNION ALL select 30 Number 
   UNION ALL select 40 Number UNION ALL select 50 Number;

+--------+
| Number |
+--------+
| 10     |
| 20     |
| 30     |
| 40     |
| 50     |
+--------+
5 rows in set (0.00 sec)

mysql> SELECT 1 a UNION ALL SELECT 2 a UNION ALL SELECT 3 a;

+---+
| a |
+---+
| 1 |
| 2 |
| 3 |
+---+
3 rows in set (0.00 sec)