Re: cheapest way to access every 15th row in table ordered by timestamp column
- From: Niall Litchfield <niall.litchfield@xxxxxxxxx>
- To: Chris.Stephens@xxxxxxx
- Date: Wed, 19 Jan 2011 18:08:43 +0000
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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