BIGINT UNSIGNED value is out of range in..的解决方法

今天在做一个功能的时候，用到两个时间戳相减来做查询条件，由于其两个字段都是unsigned的，并两个的大小是不一样。所以直接相减查询的时候，

就出现ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in..的错误，因为结果可能会出现负数。。。。

过后查资料，发现可以通过下面的方法来解决：

 

mysql> select lastvisit, lastactivity from pre_common_member_status limit 1;  
+------------+--------------+  
| lastvisit  | lastactivity |  
+------------+--------------+  
| 1199200260 |   1198336989 |  
+------------+--------------+  
1 row in set (0.01 sec)  
  
mysql> select lastvisit-lastactivity from pre_common_member_status limit 1;  
+------------------------+  
| lastvisit-lastactivity |  
+------------------------+  
|                 863271 |  
+------------------------+  
1 row in set (0.05 sec)  
  
mysql> select abs(lastvisit-lastactivity) from pre_common_member_status limit 1;  
  
+-----------------------------+  
| abs(lastvisit-lastactivity) |  
+-----------------------------+  
|                      863271 |  
+-----------------------------+  
1 row in set (0.03 sec)  
  
mysql> select lastactivity-lastvisit from pre_common_member_status limit 1;  
ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(`discuz`.`pre_c  
ommon_member_status`.`lastactivity` - `discuz`.`pre_common_member_status`.`las  
tvisit`)'  
mysql> select cast(lastactivity as signed)-cast(lastvisit as signed) from pre_co  
mmon_member_status limit 1;  
+--------------------------------------------------------+  
| cast(lastactivity as signed)-cast(lastvisit as signed) |  
+--------------------------------------------------------+  
|                                                -863271 |  
+--------------------------------------------------------+  
1 row in set (0.02 sec)  
  
mysql> select abs(cast(lastactivity as signed)-cast(lastvisit as signed)) from p  
re_common_member_status limit 1;  
+-------------------------------------------------------------+  
| abs(cast(lastactivity as signed)-cast(lastvisit as signed)) |  
+-------------------------------------------------------------+  
|                                                      863271 |  
+-------------------------------------------------------------+  
1 row in set (0.00 sec)  
  
mysql>