Question

I have data table in Oracle 8,1. There are about a million rows. But lots of rows duplicates by the same columns. I need to know fastest way to clear this data.
For example I have:

id name surname date
21 'john' 'smith' '2012 12 12'; 
21 'john' 'smith' '2012 12 13';
21 'john' 'smith' '2012 12 14';
....

And now I need to delete first two rows as they duplicates by first three columns and keep the row with the latest date.

Answer 1

If there are really lots of duplicates, I’d recommend to recreate the table with only the clean data:

CREATE TABLE tmp AS 
SELECT id, name, surname, max(d) as d
   FROM t
  GROUP BY id, name, surname;

and then replace the original table with the original table:

RENAME your_table TO old_table;
RENAME tmp_table TO your_table;

Don’t forget to move indexes, constraints and privileges…