Re: Randomizing records in a file

On 04 Jun 2012 11:58, Albert York wrote:

I have a file that contains around 12 million records. I need a way to
randomize the order of the file in the most efficient method. Does
anyone have any ideas?

As Booth asks effectively... Randomize the order of selection, or the order of physical records? Either way, the following is a fairly simple means to effect the unordered data set with a /random/ value in a column:

create view the_file_rand as
( select the_file.*, rand(r) as r
from the_file
)

Then the following SELECT can retrieve the rows in a /random/ order; that could be directed to a[n ordered] physical copy of the data:

select * /* or specify column list omitting column R */
from the_file_rand
order by r

Regards, Chuck