问：现在也有个数据统计的问题困绕着我。见如下数据，我要得到的是encode在哪几天里没有销售，求SQL语句，要考虑性能问题(表里有几百万条记录，而且每天都在增长)。
有如下的数据
sdate encode count
-------- -------- ------
2006-1-1 1001 5
2006-1-1 1002 11
2006-1-2 1002 7
2006-1-2 1003 1
2006-1-3 1003 5
2006-1-3 1003 21
2006-1-4 1001 18
2006-1-4 1002 10
现在想要得到如下形式的数据
sdate encode
-------- -------
2006-1-2 1001
2006-1-3 1001
2006-1-3 1002
create table t(sdate varchar2(10),encode numeric,count numeric)
insert into t values('2006-1-1',1001,5 )
insert into t values('2006-1-1',1002,11)
insert into t values('2006-1-2',1002,7 )
insert into t values('2006-1-2',1003,1 )
insert into t values('2006-1-3',1003,5 )
insert into t values('2006-1-3',1003,21)
insert into t values('2006-1-4',1001,18)
insert into t values('2006-1-4',1002,10)
select
a.sdate,b.encode
from
(select distinct sdate from t) a,
(select distinct encode from t) b
where
not exists(select * from t where sdate=a.sdate and encode=b.encode)
order by
b.encode,a.sdate
