Sql query-based on transactions

Question

Hi,
The below table is currently having 78,000 records and is running in the production environment, performance should be taken into account.
For example, the table is having the data in the below format.
Date     Value
22.01.08 5 PM     49
22.01.08 5:30 PM     50
22.01.08 5:45 PM     48
22.01.08 6:00 PM     45
Here the last transaction occurred at 6 PM with value 45.
I have to display the value of the previous transaction from the last transaction that is the expected output value is 48.
Kindly let me know the query how to retrieve it considering the load and performance issues.

Answer 1

CREATE TABLE TRY ("DAT" DATE,VALUE NUMBER);
alter session set nls_date_format = 'DD-MON-YYYY HH24 MI:SS';
insert into try values(sysdate,32);
insert into try values(sysdate,32);
insert into try values(sysdate,32);
insert into try values(sysdate,32);
insert into try values(sysdate,40);
insert into try values(sysdate,45);
insert into try values(sysdate,48);
insert into try values(sysdate,31);
select * from try;
DAT                       VALUE
05-MAR-2008 17 56:59         32
05-MAR-2008 17 57:26         32
05-MAR-2008 18 02:26         32
05-MAR-2008 18 02:29         32
05-MAR-2008 18 02:42         40
05-MAR-2008 18 02:45         45
05-MAR-2008 18 02:47         48
05-MAR-2008 18 02:54         31select dat,value
from (select dat,value,dense_rank() over(order by dat desc) as rank
from try)
where rank=2;
DAT                       VALUE
05-MAR-2008 18 02:47         48I hope this will work for you.