Re: cheapest way to access every 15th row in table ordered by timestamp column

What does every 15th row mean? Would only storing every 15th sample be more
appropriate?

On 19 Jan 2011 16:22, "Stephens, Chris" <Chris.Stephens@xxxxxxx> wrote:

 11.2.0.2 on Linux 5



We have a lab instrument recording information every 2 seconds into a table.



The scientists pull that data into excel for analysis (I hope to look at
this excel spreadsheet in the very near future now that I’ve read chapter 9
of Pro Oracle SQL).



They are requesting a view that picks out every 15th row of data going back
30 days.



Can anyone think of a more efficient way to do it than this:



SELECT x.col,

              x.t_stamp

      FROM ( SELECT col,

                                    t_stamp

                                   rownum rn

                         FROM t

                        WHERE t_stamp >= TRUNC( SYSDATE - 30 )) x

     WHERE MOD( x.rn, 15 ) = 0;





It feels like there should be a better way to do it.



chris

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