Last or oldest record in a oracle database table

Question

I want to fetch oldest record in database table based on llast updated date ; I tried following queries..it gave me different results
SELECT EVENT_ID, RETENTION_TS
FROM ( SELECT EVENT_ID, RETENTION_TS, RANK() OVER (ORDER BY RETENTION_TS) RETENTION_TS_RANK
FROM EVENT )
WHERE RETENTION_TS_RANK <= 1;
select * from EVENT where rowid=(select min(rowid) from EVENT);
SELECT *
FROM (select * from EVENT ORDER BY RETENTION_TS) EVENT2
WHERE rownum <= 1
ORDER BY rownum DESC;
Above query takes like 10 to 20 mins to return me the record.
Thanks in advance..

Answer 1

feritz wrote:
I want to fetch oldest record in database table based on llast updated date ; I tried following queries..it gave me different results
SELECT EVENT_ID, RETENTION_TS
FROM ( SELECT EVENT_ID, RETENTION_TS, RANK() OVER (ORDER BY RETENTION_TS) RETENTION_TS_RANK
FROM EVENT )
WHERE RETENTION_TS_RANK <= 1;
select * from EVENT where rowid=(select min(rowid) from EVENT);
THAT surely won't give a correct result. Rowid is the address of the row ... it has nothing to do with the age of the row.
What is the datatype of RETENTION_TS?
SELECT *
FROM (select * from EVENT ORDER BY RETENTION_TS) EVENT2
WHERE rownum <= 1
ORDER BY rownum DESC;
Above query takes like 10 to 20 mins to return me the record.
Thanks in advance..See "how can I improve he performance of my query" in the FAQ at https://forums.oracle.com/forums/ann.jspa?annID=1535