create_function_format_filesize.sql

CREATE FUNCTION `format_filesize`(filesize INTEGER) RETURNS varchar(20) CHARSET utf8
BEGIN

DECLARE log INT;

SET log = TRUNCATE(LOG(1024, filesize), 0);
RETURN CONCAT(ROUND(filesize / POW(1024, log), 2), ' ',
            ELT(log + 1, 'Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB', 'BB'));

END

create_function_parse_filesize.sql

CREATE FUNCTION `parse_filesize`(filesize varchar(50) CHARSET utf8) RETURNS int(11)
BEGIN

DECLARE val, exp INT;
DECLARE unit VARCHAR(10);

SET val = CAST(filesize AS UNSIGNED);
SET unit = TRIM(SUBSTRING(filesize, LENGTH(val) + 1));
SET exp = FIELD(unit, 'Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB', 'BB') - 1;

RETURN POW(1024, exp) * val;

END