[PerlChina] 有个SQL 查询，出错了。着急问一下结果

不好意思，着急用。刚才在SQL IRC里没人回答。所以发这里，望有人解决一下。

SELECT (unix_timestamp(now()) - unix_timestamp(starttime)) as diff  FROM `workers` WHERE diff < 900;

上面这条MySQL查询为什么出错？？

MySQL said:

#1054 - Unknown column 'diff' in 'where clause'



rorot Dec/04/2008