mysql中为什么用i代表分钟数

因为mysql函数，字段是不区分大小写的。因为月份month把m占用了。如果分钟再用minute的首字母的话，就无法区分是月还是分钟，所以把代表字母往后面移了一位，用第二个字母代替i代替了分钟。

now()-stime 得到的是minute * 100，这个数值的与分钟的单位换算是100=1分钟，超过60分钟这个数值无效。

得到时间差：

select (unix_timestamp(now())-unix_timestamp(stime))/60 from table_name where whew_condition

mysql>select * from timeminus

+----+---------------------+

| id | stime |

+----+---------------------+

| 1 | 2011-09-21 09:30:00 |

| 2 | 2011-09-21 11:30:00 |

| 3 | 2011-09-20 00:00:00 |

+----+---------------------+

3 rows in set (0.02 sec)

# 计算id=1与id=2的时间差（分钟）

mysql>select (unix_timestamp(a.stime)-unix_timestamp(b.stime))/60 from (select

* from timeminus where id=2) a inner join (select * from timeminus where id=1) b

+------------------------------------------------------+

| (unix_timestamp(a.stime)-unix_timestamp(b.stime))/60 |

+------------------------------------------------------+

| 120.0000 |

+------------------------------------------------------+

1 row in set (0.00 sec)

---