有道笔试题：

服务器监控表server_status中,当服务器状态发生server_status变化时数据表中将被插入一条记录,状态0表示停机 1表示正常,用SQL查询Server A 的停机开始时间和结束时间,表中存在多台Server的状态记录.

SVR_ID　 SVR_NAME STATUS_TIME STATUS
1 A 2013-10-31 00:00:00 1
2 B 2013-10-31 00:00:00 1
1 A 2014-11-31 00:00:00 0
2 B 2014-11-31 00:00:00 0
3 C 2014-11-31 00:00:00 0
... ... ... ...

我做的话只会

select s1.svr_name, s1.status_time start_date, s2.status_time end_date
from server_status s1, server_status s2
where s1.svr_id = s2.svr_id
and s1.status = 1
and s2.status = 0

and s1.svr_name='A'

，今天看到别人用了case when语法，于是我也试着写了一下

select svr_name,
case status
when 1 then
status_time
end as start_time,
case status
when 0 then
status_time
end as end_time
from server_status
where svr_name = 'A'
不知道有没有更好的做法...