RE: cheapest way to access every 15th row in table ordered by timestamp column
- From: <Dominic.Brooks@xxxxxxxxxxxxxxxxxxx>
- To: <Chris.Stephens@xxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 19 Jan 2011 16:33:23 +0000
SAMPLE clause is another option if you want a random percentage of the data...
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Stephens, Chris
Sent: 19 January 2011 16:20
To: ORACLE-L
Subject: cheapest way to access every 15th row in table ordered by timestamp
column
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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