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May 19, 2010 at 0:32 comment added Jeffrey Kemp Yeah. Sujee beat me to the ROWNUM solution which is better :)
May 18, 2010 at 8:15 comment added Rob van Wijk It avoids scanning the table twice, but it calculates the first_value column for every row, and then the distinct discards them all but one. Better than most other answers, but aggregating is the way to go here.
May 18, 2010 at 5:41 comment added Jeffrey Kemp If you have an index on (value_col, date_col) you'll find that Oracle will do quite well using Sujee's query, since it will use the COUNT STOPKEY optimization.
May 18, 2010 at 4:22 comment added TerrorAustralis I would be interested in seeing what kind of performance difference this had, from a purely educational point of view. From Toms asktom.oracle site i had understood there were significant overheads in using FIRST_VALUE. Is it possible that you could direct me to some performance results comparing them?
May 18, 2010 at 4:04 history answered Jeffrey Kemp CC BY-SA 2.5