Bonanza.sql

delimiter //
CREATE PROCEDURE Bonanza()
BEGIN
  SELECT name FROM user WHERE id = TRUNCATE(RAND() * (
      SELECT MAX(id) FROM user
  )+ .9, 0); 
END
//
delimiter ;

User.sql

CREATE TABLE user (
  id TINYINT AUTO_INCREMENT,
  name VARCHAR(100),
  PRIMARY KEY(id)
)

$ mysql

source Bonanza.sql;
source User.sql;
INSERT INTO user (name) VALUES ("hogehoge");
INSERT ...
call Bonanza();