使用将字符串转换为时间戳 from_unixtime() . 它会在短时间内运行良好 VARCHAR 列。
例子：

create table mytable (oldts varchar(10), newts timestamp NULL);

insert into mytable (oldts,newts) values ('1246251403', NULL);
insert into mytable (oldts,newts) values ('1246251404', NULL);
insert into mytable (oldts,newts) values ('1246251404', NULL);

update mytable SET newts = from_unixtime(oldts);

select oldts, newts from mytable;

结果：

|      oldts |                newts |
|------------|----------------------|
| 1246251403 | 2009-06-29T04:56:43Z |
| 1246251404 | 2009-06-29T04:56:44Z |
| 1246251404 | 2009-06-29T04:56:44Z |

sql小提琴