问题
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
How to retrieve the maximum process_date from Table_C with references of Table_A.A_id based on Table_C timing window. If I want to retrieve Table_C.b_id and max(process_date) in timing window 20130101 12:09:00 to 12:21:00 then it should return id as 1 and process_date as 12:20:01
Below query Is i am using:
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;
回答1:
If I follow, you want the maximum process date and corresponding b_id for a given a_id where the process date is within a set date range. Here is a solution not requiring any analytic functions or row number. I'm using a with clause and dual just to replicate your sample tables. You can remove that if you have table_a, table_b, table_c.
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')
)
returns:
----------------------------
b_id | process_date
----------------------------
1 1/1/2013 12:20:01
来源：https://stackoverflow.com/questions/15259989/how-to-improve-oracle-row-number-in-query