2018-07-08 8:19 GMT+02:00 Cecil Westerhof <[email protected]>:
> I thought there was a problem with RANDOM. I used:
> , ABS(RANDOM()) / CAST(1.4E18 AS INTEGER) AS Randomiser
>
> And it seemed I got a lot of threes.
>
> To check this I used:
> SELECT Randomiser
> , COUNT(*) AS Count
> FROM (
> SELECT date
> , ABS(RANDOM()) / CAST(1.4E18 AS INTEGER) AS Randomiser
> FROM CPUUsage
> ORDER BY date
> )
> GROUP BY Randomiser
> ORDER BY Randomiser
>
> And this gave results like:
> "0" "165491"
> "1" "166270"
> "2" "166207"
> "3" "165727"
> "4" "165619"
> "5" "165749"
> "6" "98042"
>
> So 6 is created less often as 0 - 5, but that is in my use case not a
> problem.
>
> This worked for me because I have a big table CPUUsage. But if I would not
> have, is there another way to to do this?
>
By the way better select is:
SELECT Randomiser
, COUNT(*) AS Count
FROM (
SELECT date
, CAST(ABS(RANDOM()) / (9.223E18 / 7) AS INTEGER) AS
Randomiser
FROM CPUUsage
ORDER BY date
)
GROUP BY Randomiser
ORDER BY Randomiser
This gives:
"0" "156204"
"1" "157032"
"2" "155636"
"3" "156399"
"4" "156256"
"5" "155480"
"6" "156073"
"7" "52"
This is much better. Only very rarely you get a seven you do not want.
(Again in my case not really a problem.)
Because in my case I use Randomiser to get a small subset of the records,
this can be solved with:
SELECT Randomiser
, COUNT(*) AS Count
FROM (
SELECT date
, CAST(ABS(RANDOM()) / (9.223E18 / 7) AS INTEGER) AS
Randomiser
FROM CPUUsage
ORDER BY date
)
WHERE Randomiser <> 7
GROUP BY Randomiser
ORDER BY Randomiser
Then I get something like:
"0" "155806"
"1" "156270"
"2" "156473"
"3" "155748"
"4" "155828"
"5" "156196"
"6" "156733"
--
Cecil Westerhof
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