Question

Table_A
-------------------
A_id          
-------------------
1     

Table_B
-------------------
B_id   |     A_id
-------------------
1            1
2            1
3            1

Table_C
-----------------------------
B_id  |   Process_date
-----------------------------
1         20130101 12:20:01
2         20130101 12:10:01
3         20130101 13:00:01

如何根据process_date时间窗口引用Table_C，从Table_A.A_id检索最大Table_C。如果我想在时间窗口Table_C.b_id中检索max(process_date)和20130101 12:09:00到12:21:00，则应将id返回为1，将process_date返回为12:20:01

以下查询我正在使用：

select b_id, 
       process_date
  from (select c1.b_id,
               c1.process_date,
               row_number() over(partition by a.a_id 
                                 order by c1.process_date desc) rn
          from table_a a
               inner join 
               table_b b
                 on a.a_id = b.a_id
               inner join 
               table_c c1
                 on b.b_id = c1.b_id
       ) 
 where rn = 1;

Answer 1

如果我关注，您需要最大处理日期和给定a_id的相应b_id，其中处理日期在设定的日期范围内。这是一个不需要任何分析功能或行号的解决方案。我正在使用with子句和dual来复制样本表。如果你有table_a，table_b，table_c。

，你可以删除它

with table_a as 
(
 select 1 a_id from dual
),
table_b as 
(
 select 1 b_id, 1 a_id from dual union all
 select 2 b_id, 1 a_id from dual union all
 select 3 b_id, 1 a_id from dual
), table_c as
(
 select 1 b_id, to_date('20130101 12:20:01', 'yyyymmdd hh24:mi:ss') process_date from dual union all
 select 2 b_id, to_date('20130101 12:10:01', 'yyyymmdd hh24:mi:ss') process_date from dual union all
 select 3 b_id, to_date('20130101 13:00:01', 'yyyymmdd hh24:mi:ss') process_date from dual
) 
select table_c.b_id, 
       table_c.process_date
  from table_b,
       table_c
 where table_b.b_id = table_c.b_id
   and table_b.a_id = 1
   and table_c.process_date = (select max(process_date)
                                 from table_b b2,
                                      table_c c2
                                where table_b.a_id = b2.a_id
                                  and b2.b_id = c2.b_id
                                  and c2.process_date between to_date('20130101 12:09:00', 'yyyymmdd hh24:mi:ss')  and 
                                                              to_date('20130101 12:21:00', 'yyyymmdd hh24:mi:ss')
                              )

返回：

----------------------------
b_id  |  process_date
----------------------------
1       1/1/2013 12:20:01

如何在查询中改进oracle row_number

1 个答案: