MySql - Calculating percentile ranks on the fly
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I have a MySql SELECT query which uses 20 different comparisons within the same table. Here's an example:

    SELECT * FROM mytable
    WHERE (col1 > (col2 * 0.25))
    AND (col5 < col10) .......

I'm trying to calculate percentile ranks based on the order of a column called `SCORE` within the `SELECT` results returned. I've tried using incremental row numbers and `COUNT(*)` to get the stock's rank and total number of results returned but not sure how to assign the same rank where some of the results have the same `SCORE`.

Here's the formula that I'm trying to calculate:

    ((COUNT(lower scores) + (COUNT(same/tied scores) / 2)) * 100) / COUNT(total results)

How do I find the number of lower scores, same/tied scores and total scores within the same result row for calculating percentiles on the fly?

I'm trying to avoid using stored procedures because I want to my application's admins to tailor the SELECT statement within my applications admin area as needed.