如何将 INTERVAL 关键字与 MySQL NOW() 和 CURDATE() 函数一起使用？

mysql> Select NOW() + INTERVAL 2 day;
+------------------------+
| NOW() + INTERVAL 2 day |
+------------------------+
| 2017-10-30 09:19:31    |
+------------------------+
1 row in set (0.00 sec)

mysql> Select NOW() - INTERVAL 2 day;
+------------------------+
| NOW() - INTERVAL 2 day |
+------------------------+
| 2017-10-26 09:19:45    |
+------------------------+
1 row in set (0.00 sec)

mysql> Select NOW() - INTERVAL 2 hour;
+-------------------------+
| NOW() - INTERVAL 2 hour |
+-------------------------+
| 2017-10-28 07:19:51     |
+-------------------------+
1 row in set (0.00 sec)

mysql> Select CURDATE() - INTERVAL 2 day;
+----------------------------+
| CURDATE() - INTERVAL 2 day |
+----------------------------+
| 2017-10-26                 |
+----------------------------+
1 row in set (0.00 sec)

mysql> Select CURDATE() + INTERVAL 2 day;
+----------------------------+
| CURDATE() + INTERVAL 2 day |
+----------------------------+
| 2017-10-30                 |
+----------------------------+
1 row in set (0.00 sec)