不多说
表：table1｛id,app_id,create_user,create_time｝
app_id 和 create_user 相同的为重复数据 （即两条数据，app_id相等，并且cureate_user相等，那么就是有重复数据）
要留 create_time 最大（最新）的数据，删除其他重复的。
上语句 满分， 带解释的，加分
------解决方案--------------------
代码不是太长，看一下吧。
不理解，再问我。呵呵
declare
v_appid varchar2(100) := "";
cursor mycur is
select id,app_id,create_user,create_time from table1
order by app_id,create_time desc;
r_mycur table1%rowtype;
begin
open mycur;
loop
fetch mycur into r_mycur;
exit when mycur%notfound;
if(v_appid = r_mycur.app_id) then
delete table1
where app_id = r_mycur.app_id
and create_time = r_mycur.app_id;
end if;
v_appid := r_mycur.app_id;
end loop;
close mycur;
commit;
end;
------解决方案--------------------
- SQL code
create table table1(id int,app_id int,create_user varchar2(10),created_time date);
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- SQL code
delete from table1 where id in (select id from (select t.id, t.create_time, max(create_time) over(partition by app_id, create_user) maxtime,--按app_id, create_user分组取最大时间 count(1) over(partition by app_id, create_user) grpcnt --计算按app_id, create_user分组时每组中的记录条数 from table1 t order by id) t where t.grpcnt > 1 and t.create_time = t.maxtime)
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- SQL code
witht1 as (select id,app_id,count(*) cnt from table1 group by id,app_id having count(*)>1), --查找重复记录t2 as (select id,app_id,max(create_time) c_time from table1 group by id,app_id), --查找最大时间t3 as (select t1.id,t1.app_id,t2.c_time from t1,t2 where t1.id=t2.id and t1.app_id=t2.app_id), --关联重复记录的最大时间delete from table1 a where exists (select 1 from t3 where a.id=t3.id and a.app_id=t3.app_id and a.create_time<>t3.c_time) --删除不是最大时间的记录
------解决方案--------------------
- SQL code
CREATE TABLE test(id VARCHAR2(10),app_id VARCHAR2(10),create_user VARCHAR2(50),create_time VARCHAR2(30));INSERT INTO test VALUES ('1','1','jack','20120601 12:01:00');INSERT INTO test VALUES ('2','1','jack','20120601 12:50:00');INSERT INTO test VALUES ('3','1','jack','20120601 23:01:00');INSERT INTO test VALUES ('4','1','rose','20120615 12:01:00');INSERT INTO test VALUES ('5','1','rose','20120616 12:01:00');DELETE FROM test t WHERE NOT EXISTS (SELECT 1 FROM (SELECT DISTINCT app_id,create_user, Last_Value(create_time) over (PARTITION BY app_id,create_user ORDER BY create_time rows between unbounded preceding and unbounded following)create_time FROM test ) WHERE app_id=t.app_id AND create_user=t.create_user AND create_time=t.create_time )SELECT * FROM test;ID, APP_ID, CREATE_USER, CREATE_TIME3 1 jack 20120601 23:01:005 1 rose 20120616 12:01:00
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