表描述:table_yyy ,两个关键字段 devid , time
devid time desc
1 20080910 xx
1 20081013 xx
1 20081021 xx
2 20080913 xx
3 20080910 xx
3 20081013 xx需要查询出最接近当前时间的,各个设备的的记录!
查询结果
devid time desc
1 20081021 xx
2 20080913 xx
3 20081013 xxsql语句怎么写,谢谢!
devid time desc
1 20080910 xx
1 20081013 xx
1 20081021 xx
2 20080913 xx
3 20080910 xx
3 20081013 xx需要查询出最接近当前时间的,各个设备的的记录!
查询结果
devid time desc
1 20081021 xx
2 20080913 xx
3 20081013 xxsql语句怎么写,谢谢!
where not exists (
select 1
from table_yyy
where devid=y.devid
and time>y.time
)
(select devid, max(time) as time from table_yyy group by devid)b
where a.devid=b.devid and a.time=b.time
select * from table_yyy a where not exists(select 1 from table_yyy where device=a.device and time>a.time) order by desc
第二种
select * from table_yyy a where time=(select max(time) from table_yyy where device=a.device) order by desc
试试行不行吧