关于一个电灯开关时间统计的需求
南角影 2010-01-05 07:33:28 这样的需求,应该如何实现
有某个公司,想评估一下某日或者几日走廊电灯开关的使用间隔,还有每日电灯使用时间,开关次数
现有数据库表记录开关时间,可以用SQL直接求出 电灯的开启间隔 与 使用时间吗?
目前设计仅有一张表,并且每次开关操作没有唯一标识
表结构如下
create table switch_recd(flag int, time timestamp);
COMMENT ON COLUMN switch_recd.flag IS '开关标志,0开 1关';
COMMENT ON COLUMN switch_recd.time IS '操作时间';
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
insert into switch_recd values(0,current timestamp);
insert into switch_recd values(1,current timestamp);
select * from switch_recd;