Calculating percentiles for each data record

[Ryan Huff]

I have a semi-large table (2000-3000 records and growing) in which I have stored a decimal for each row. This number is an *absolute* rating score for the record. I'd like to derive from this a *relative* rating for each record from .5-10, in .5 increments.

So I need to calculate which PERCENTILE each record is in, and assign the relative score accordingly.

For instance, if a record has a score of 1234.5, and I find that it's in the 65th percentile (65% of records have absolute scores <= 1234.5), then I would assign it a relative score of 6.5.

My question is, how do I figure the percentile score for each record?

I anticipate that this will be run as a batch process on a nightly basis, but I'm open to suggestions.

THANKS in advance!
- Ryan