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just a note about Db2's RAND() function
https://stackoverflow.com/questions/36209123/random-function-in-db2-is-not-evenly-distributed/36209627#36209627


I really need to see if that's still the case :)

Charles


On Wed, Oct 2, 2019 at 12:49 PM Booth Martin <booth@xxxxxxxxxxxx> wrote:

A large file,say a million records in which there are about 12,000
records with a "W" in Field20. I want 10 random records from the
12000. I can't figure out how to write the WHERE clause so that only
records from the 12,000 will be included .

Here's what I use for random hits on the big file:

exec sql select rand(MICROSECOND(CURRENT_TIMESTAMP)) into :wField5
from SYSIBM/SYSDUMMY1;
wSeed = wField5 * 10000;
//
---------------------------------------------------------------------
// Get 10 random numbers
clear wCount;
wNdx = 0;
dow wNdx < 10 and wCount < 1200; // (if we can't get 10 in
1200, bail)
wCount += 1;
exec sql select rand(:wSeed) into :wField5
from SYSIBM/SYSDUMMY1;
wSeed = wField5 * 10000;
exec sql select FIELD1 into :wField1
from FILE01
where rrn(FILE01) = :wSeed;

...

"where rrn(FILE01) = :wSeed and FIELD20 = 'W';" seems easy but somehow
wrong.

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