mysql UNIX_TIMESTAMP的使用

UNIX_TIMESTAMP是从1970-01-01 08:00:00开始比较，看后来的时间比这个时间多多少秒

mysql> SELECT UNIX_TIMESTAMP('1970-01-01 08:02:00');
+---------------------------------------+
| UNIX_TIMESTAMP('1970-01-01 08:02:00') |
+---------------------------------------+
|                                   120 | 
+---------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT UNIX_TIMESTAMP('1970-01-01 07:02:00');
+---------------------------------------+
| UNIX_TIMESTAMP('1970-01-01 07:02:00') |
+---------------------------------------+
|                                     0 | 
+---------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT UNIX_TIMESTAMP(20130101);
+--------------------------+
| UNIX_TIMESTAMP(20130101) |
+--------------------------+
|               1356969600 | 
+--------------------------+
1 row in set (0.00 sec)