create table TEST (USER_ID NUMBER,TYPE_ID NUMBER,PRICE NUMBER,CREATE_TIME DATE);

insert into TEST values (1,1,199,date'2012-01-01');
insert into TEST values  (2,2,299,date'2012-01-01');
insert into TEST values  (3,2,299,date'2012-01-01');
insert into TEST values  (4,1,199,date'2012-01-01');
insert into TEST values  (1,3,399,date'2012-01-11'); 
insert into TEST values  (1,4,499,date'2012-01-11');
insert into TEST values  (3,3,399,date'2012-02-01');
insert into TEST values  (1,5,599,date'2012-02-01');
insert into TEST values  (4,2,299,date'2012-02-01');
insert into TEST values  (4,3,399,date'2012-02-01');
insert into TEST values  (4,4,499,date'2012-02-01');
insert into TEST values  (5,3,399,date'2012-03-01');
insert into TEST values  (1,4,499,date'2012-03-01');
insert into TEST values  (1,3,399,date'2012-04-01');
insert into TEST values  (2,4,499,date'2012-04-01');
       
--(1) 查出表中不同的用户总数
select count(distinct USER_ID) c_user
from TEST;

--(2) 查出本月销售总额
select sum(PRICE) s_price
from TEST
where to_char(sysdate,'yyyy-mm')=to_char(CREATE_TIME,'yyyy-mm')

--（3) 查出每天的(不同)用户数，总购买次数，销售额
select CREATE_TIME,count(distinct USER_ID) c_user,count(TYPE_ID) c_type,sum(PRICE) s_price
from TEST
group by CREATE_TIME

------解决方案--------------------
--（3) 查出每天的(不同)用户数，总购买次数，销售额
select CREATE_TIME,count(distinct USER_ID) c_user,count(TYPE_ID) c_type,sum(PRICE) s_price
from TEST
group by CREATE_TIME


这个有问题，购买次数不能按 商品来算，应该按 购买时间来算。

------解决方案--------------------
探讨


--（3) 查出每天的(不同)用户数，总购买次数，销售额
select CREATE_TIME,count(distinct USER_ID) c_user,count(TYPE_ID) c_type,sum(PRICE) s_price
from TEST
group by CREATE_TIME


这个有问题，购买次数不能按 商品来算，应该按 购买时间来算。