下面语句怎么写?谢谢!
"aid","bid","date1","exchage"
"a","b",2005-01-01 00:00:00,"0.1"
"a","c",2005-01-01 00:00:00,"0.2"
"a","d",2005-01-01 00:00:00,"0.3"
"a","e",2005-01-01 00:00:00,"0.5"
"b","a",2005-03-01 00:00:00,"0.5"
"b","c",2004-03-01 00:00:00,"0.6"
"b","d",2005-03-01 00:00:00,"0.8"
"c","a",2005-04-05 00:00:00,"0.1"
"c","b",2005-04-05 00:00:00,"0.5"
"c","d",2005-04-05 00:00:00,"0.2"
"c","e",2005-04-05 00:00:00,"0.2"
"e","a",2004-01-02 00:00:00,"0.1"
"e","h",2004-02-01 00:00:00,"0.5"
"a","b",2005-08-01 00:00:00,"0.1"
"a","c",2005-08-01 00:00:00,"0.2"
"a","d",2005-08-01 00:00:00,"0.3"
"a","e",2005-08-01 00:00:00,"0.5"
"c","b",2005-07-01 00:00:00,"0.1"
"c","a",2005-07-01 00:00:00,"01"
"c","d",2005-07-01 00:00:00,"0.4"
"c","e",2005-07-01 00:00:00,"0.4"
"d","a",2005-08-01 00:00:00,"0.5"
"d","b",2005-08-01 00:00:00,"0.8"
"d","c",2005-08-01 00:00:00,"0.4"
"d","e",2005-08-01 00:00:00,"0.5"
"d","a",2004-01-01 00:00:00,"0.3"
"d","c",2004-01-01 00:00:00,"0.5"
"d","c",2004-01-01 00:00:00,"0.6"
"d","a",2005-01-01 00:00:00,"0.1"
"d","c",2005-01-01 00:00:00,"014"
"d","b",2005-01-01 00:00:00,"0.4"
"d","e",2005-01-01 00:00:00,"0.6"
我想得到如下结果怎么做?也就是aid每天重复4次,并且date1是最新的日期的记录.谢谢!
"aid","bid","date1","exchage"
"a","b",2005-08-01 00:00:00,"0.1"
"a","c",2005-08-01 00:00:00,"0.2"
"a","d",2005-08-01 00:00:00,"0.3"
"a","e",2005-08-01 00:00:00,"0.5"
"c","b",2005-07-01 00:00:00,"0.1"
"c","a",2005-07-01 00:00:00,"01"
"c","d",2005-07-01 00:00:00,"0.4"
"c","e",2005-07-01 00:00:00,"0.4"
"d","a",2005-08-01 00:00:00,"0.5"
"d","b",2005-08-01 00:00:00,"0.8"
"d","c",2005-08-01 00:00:00,"0.4"
"d","e",2005-08-01 00:00:00,"0.5"