[Fwd: Re: surprising results with random()]

John R Pierce <pierce@hogranch.com> writes:

ries van Twisk wrote:

should the function not look like this???

CREATE OR REPLACE VIEW test_view AS
SELECT
CASE
WHEN random() < .333333333 THEN '1'
WHEN random() < .5 THEN '2'
ELSE '3'
END AS test_value

FROM client;

actually, I'd think that should be .66666

Nah, ries is correct. Think of it this way: one-third of the time the
first WHEN succeeds, and you get '1'. In *half of the remaining cases*,
you want '2', so the second test should be against 0.5.

but... wouldn't floor(random() * 3.0) + 1 be a simpler way to do this?

Agreed...

regards, tom lane