int（11）;

mysql> create table UnixTime
   -> (
   -> DueTime datetime
   -> );
Query OK，0 rows affected（0.55 sec）

mysql> insert into UnixTime values（now（））;
Query OK，1 row affected（0.15 sec）

mysql> insert into UnixTime values（'2010-10-14'）;
Query OK，1 row affected（0.15 sec）

mysql> insert into UnixTime values（'2020-09-24'）;
Query OK，1 row affected（0.15 sec）

mysql> select *from UnixTime;

+ --------------------- +
| DueTime |
+ --------------------- +
| 2018-12-19 10:07:11 |
| 2010-10-14 00:00:00 |
| 2020-09-24 00:00:00 |
+ --------------------- +
3行(0.00秒内)

mysql> select unix_timestamp(DueTime) as Output from UnixTime;

+------------+
| Output     |
+------------+
| 1545194231 |
| 1286994600 |
| 1600885800 |
+------------+
3 rows in set (0.00 sec)