Select TOP X (or bottom) percent for numeric values in MySQL

Question

I was wondering if there are any functions that can be used in MySQL to select the TOP X(or bottom) percent from a column containing numeric values.

Basically, I ha

Answer 1

UPDATE: Much more thought-out explanation of the subject from much more knowing person here. Nonetheless, it still seems there's no embedded function in MySQL to calculate percentiles.

Try:

SELECT * FROM prices WHERE price >= (SELECT 0.9 * max(price) FROM prices)

SELECT price FROM prices p1 WHERE
(SELECT count(*) FROM prices p2 WHERE p2.price >= p1.price) <=
     (SELECT 0.1 * count(*) FROM prices)
);

This will give price P1 for which number of records in Price table having price >= P1 will be one tenth of total number of records in Price table. After that:

SELECT * FROM prices WHERE price >= (SELECT price FROM prices p1 WHERE
(SELECT count(*) FROM prices p2 WHERE p2.price >= p1.price) <=
     (SELECT 0.1 * count(*) FROM prices)
);

will return all desired records.

Note: I didn't examine performance of this query, I think solution with temporary table/variable must be more effective.

Answer 2

EDIT - new answer

Answered in Convert SQL Server query to MySQL

Select *
from
(
    SELECT tbl.*, @counter := @counter +1 counter
    FROM (select @counter:=0) initvar, tbl
    ORDER BY ordcolumn
) X
where counter <= (50/100 * @counter);
ORDER BY ordcolumn

---

OLD ANSWER

For MySQL, you could calculate the batch size required and then LIMIT to that number of records

SELECT @rows := ROUND(COUNT(*) * 10/100) FROM table;
PREPARE STMT FROM ‘SELECT * FROM tbl ORDER BY price LIMIT ?’;
EXECUTE STMT USING @rows;

For a bottom percent, just order in reverse

SELECT @rows := ROUND(COUNT(*) * 10/100) FROM table;
PREPARE STMT FROM ‘SELECT * FROM tbl ORDER BY price DESC LIMIT ?’;
EXECUTE STMT USING @rows;

Oops, maybe the DESC belongs in the first query, but you get the meaning.

Note For SQL Server, the TOP N PERCENT clause certainly helps

select top 10 PERCENT *
FROM TBL
ORDER BY price

Answer 3

just as an FYI (i know this question is a few years old), this can be done other, cleaner ways as well.

SELECT * FROM product_table WHERE price >= (SELECT price FROM product_table 
ORDER BY price DESC LIMIT 1 OFFSET (SELECT 0.1 * COUNT(*) FROM product_table));

i ran a similar query over a very large database, and it ran very quickly.