CREATE TABLE `test` (
	`id` BIGINT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`content` TEXT NOT NULL,
	PRIMARY KEY (`id`)
)
COLLATE='utf8_general_ci'
ENGINE=MyISAM

CREATE DEFINER=`Monitor`@`%` TRIGGER `test_before_insert` AFTER INSERT ON `test` FOR EACH ROW BEGIN
DECLARE n integer;
DECLARE m integer;
select count(*) into @n from test;
  if @n = 10 then begin
    select min(test.id) into @m from test;
    delete from test where test.id = @m;
    end;
  end if;
END

CREATE DEFINER=`12345`@`%` PROCEDURE `tst_proc`(IN `number` INT)
	LANGUAGE SQL
	NOT DETERMINISTIC
	MODIFIES SQL DATA
	SQL SECURITY DEFINER
	COMMENT ''
BEGIN
DECLARE n, cnt, m, d INT;
SET @cnt = number;
SELECT count(tst.id) into @n from tst;
  if @n > @cnt then begin 
  SET d = @n - @cnt;
		SET @m = (SELECT tst.id
		FROM tst
		ORDER BY tst.id ASC 
		LIMIT d, 1);
		DELETE FROM tst WHERE tst.id < @m;
  		end;
  end if;
END