取出表同一类型的指定范围记录

创建测试表

create table test_tb
as
select user_id,user_name,type_id,user_time
 from (
  select 1 user_id,'aa' user_name,3 type_id,'2009-09-01' user_time from dual
  union
  select 2,'bb',3,'2009-09-02' from dual
  union
  select 3,'cc',3,'2009-09-04' from dual
  union
  select 4,'caec',5,'2009-09-02' from dual
  union
  select 5,'cdeefc',5,'2009-09-20' from dual
  union
  select 6,'acsfc',5,'2009-09-12' from dual
  union
  select 7,'csfc',5,'2009-09-22' from dual
  union
  select 8,'caaac',7,'2009-09-24' from dual
)a order by type_id,user_time desc

目的:获取每种type_id最新的两个用户

方法一,

select A.user_id,A.user_name,A.type_ID,A.user_time from
test_tb A
LEFT JOIN test_tb B
ON A.TYPE_ID=B.TYPE_ID AND A.user_id <=B.user_id
GROUP BY A.user_id,A.user_name,A.type_ID,A.user_time
HAVING COUNT(a.user_id) <=2
order by a.type_Id,a.user_id

方法二,
select A.user_id,A.user_name,A.type_ID,A.user_time from (
  select rank() over (partition by type_Id order by user_id desc)  Rank, a.* from test_tb a
)a where a.rank<=2 order by type_ID,user_id