SQL (Oracle) 查询具有最大日期的记录，仅当 end_dt 有值时

Question

I am trying to select a record from a row by looking at both the start date and the end date. What I need to do is pick the max start date, then only return a result from that max date if the end date has a value.

I hope the images below help clarify this a bit more. This is in Oracle based SQL.

Example #2

I can, so far, either return all the records or incorrectly return a record in scenario #2 but I've yet to figure out the best way to make this work. I would greatly appreciate any assistance.

Thank you!

Answer 1

I would use an analytic function:

with sample_data as (select 1 id, 1 grp_id, to_date('01/01/2015', 'dd/mm/yyyy') st_dt, to_date('23/01/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 2 id, 1 grp_id, to_date('24/02/2015', 'dd/mm/yyyy') st_dt, to_date('15/02/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 3 id, 1 grp_id, to_date('17/03/2015', 'dd/mm/yyyy') st_dt, to_date('30/03/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 4 id, 2 grp_id, to_date('01/01/2015', 'dd/mm/yyyy') st_dt, to_date('17/01/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 5 id, 2 grp_id, to_date('21/01/2015', 'dd/mm/yyyy') st_dt, to_date('23/03/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 6 id, 2 grp_id, to_date('14/04/2015', 'dd/mm/yyyy') st_dt, to_date('16/05/2015', 'dd/mm/yyyy') ed_dt from dual union all
                     select 7 id, 2 grp_id, to_date('28/05/2015', 'dd/mm/yyyy') st_dt, null ed_dt from dual),
             res as (select id,
                            grp_id,
                            st_dt,
                            ed_dt,
                            max(st_dt) over (partition by grp_id) max_st_dt
                     from   sample_data)
select id,
       grp_id,
       st_dt,
       ed_dt
from   res
where  st_dt = max_st_dt
and    ed_dt is not null;


        ID     GRP_ID ST_DT      ED_DT     
---------- ---------- ---------- ----------
         3          1 17/03/2015 30/03/2015

Answer 2

This would be one of the simplest way.

select * from
(
select apay_id,
       max(start_dt) OVER () max_start_dt,
        start_dt,
       end_dt
from sample
)
where
start_dt=max_start_dt
and end_dt is not null

Idea is to get maximum start_dt and corresponding end_dt. And then filter result if end_dt is null.

SQL Fiddle

Database Schema

create table sample
(apay_id number(7),
 account_number number(7),
 start_dt date,
 end_dt date);

Sample1

 insert into sample values(554433, 123456, '15-Aug-15', null);
 insert into sample values(112266, 123456, '21-Jul-15', '31-Aug-15');
 insert into sample values(733221, 123456, '29-Jun-15', '31-Jul-15');

Output for Sample1

No rows

Sample2

 insert into sample values(554433, 123456, '15-Aug-15', '11-Nov-15');
 insert into sample values(112266, 123456, '21-Jul-15', '31-Aug-15');
 insert into sample values(733221, 123456, '29-Jun-15', '31-Jul-15');

Output for Sample2

| APAY_ID |             MAX_START_DT |                     END_DT |
|---------|--------------------------|----------------------------|
|  554433 | August, 15 2015 00:00:00 | November, 11 2015 00:00:00 |

Answer 3

select * from ( select apay_id from sample where end_dt is not null order by start_dt desc) where rownum=1

I think this can also work.