如题,如何从一个表中查询最新的来自不同地区的四条记录
解决方案 »
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北京 2010-01-25
北京 2010-02-01
天津 2009-03-01
天津 2009-03-02
四川 2008-08-21
山东 2007-01-01
那我就取
北京 2010-01-11
天津 2009-03-01
四川
山东
order by t.time limit....如果是oracle,需要使用rownum或者按楼上有位童鞋的使用row_number()分析函数!
(
select '北京' as region,to_date('2010-01-11','yyyy-mm-dd') time from dual union all
select '北京' as region,to_date('2010-01-25','yyyy-mm-dd') time from dual union all
select '北京' as region,to_date('2010-02-01','yyyy-mm-dd') time from dual union all
select '天津' as region,to_date('2009-03-01','yyyy-mm-dd') time from dual union all
select '天津' as region,to_date('2009-03-02','yyyy-mm-dd') time from dual union all
select '四川' as region,to_date('2008-08-21','yyyy-mm-dd') time from dual union all
select '山东' as region,to_date('2007-01-01','yyyy-mm-dd') time from dual
)
select region,time from (select row_number() over(partition by region order by time desc) x, region,time from t1) a where x =1