Can't get MySQL function to work - mysql

Question

Ok so I'm making this little excercise in MySQL. I'm a pokemon trainer that needs to have a record of wins and loses, who I battled and the money earned. Everything goes all dandy until I get to this part:
*Create a function that calculates the earnings, if the battle was won then the earnings increase, if the battle was a loss then earnings decrease.
I assign the rival trainers with a "class" from 1 to 4, each trainer gives a certain amount of money
1.- 250
2.- 500
3.- 1000
4.- 2000
My tables structures go more or less like this:
battle(idBattle, idTrainer, outcome, date, place)
Trainer(idTrainer, nameTrainer, class)
protagonist(idProtagonist, loses, wons, earnings)
I need to check on the outcome of the battle to know if my earnings will increase or decrease, then go to my table Trainer and check the class to see how much is the class worth, then return how much will I increase or decrease my earnings.
Also I want to create a trigger that automatically updates my table(ie. the main trainers table) when a new win or loss has been entered as well as updating the earnings. I'll leave the code bellow, I'm all dried out and have no idea what to do now. I'm pretty much desperate. I may have been looking at this problem from the worng angle, just need some advise.
MANY, MANY THANKS IN ADVANCE IF YOU CAN HELP ME OUT!
CREATE DATABASE ricardoRifa;
USE ricardoRifa;
CREATE TABLE entrenador (//trainer table
idEntrenador INT NOT NULL DEFAULT 98000,
nombreEntrenador VARCHAR(20),
clasificacion INT NOT NULL DEFAULT 1, //this is the trainer class
PRIMARY KEY (idEntrenador)
) ENGINE=INNODB;
CREATE TABLE batalla (
idBatalla INT NOT NULL AUTO_INCREMENT,
idEntrenador INT,
resultado BOOLEAN, //false=lost battle, true=won
lugar VARCHAR(20),
fecha DATE,
PRIMARY KEY (idBatalla , idEntrenador),
CONSTRAINT fk_idEntrenador FOREIGN KEY (idEntrenador)
REFERENCES entrenador (idEntrenador)
ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE=INNODB;
CREATE TABLE ricardo (//main trainer table, I wanted it to be like this for there may be more than one instance depending on the main trainer id
idRicardo INT NOT NULL DEFAULT 11490677,
perdidas INT NOT NULL DEFAULT 0,
victorias INT NOT NULL DEFAULT 0,
ganancias INT NOT NULL DEFAULT 10000,
PRIMARY KEY (idRicardo)
) ENGINE=INNODB;
delimiter |
CREATE PROCEDURE incersionEntrenador(idEntrenador INT, nombreEntrenador VARCHAR(20), clasificacion INT)
BEGIN
INSERT INTO entrenador VALUES(idEntrenador, nombreEntrenador, clasificacion);
END |
delimiter |
CREATE PROCEDURE incersionBatalla(idEntrenador INT, resultado BOOLEAN, lugar VARCHAR(20), fecha DATE)
BEGIN
INSERT INTO batalla (idEntrenador, resultado, lugar, fecha) VALUES(idEntrenador, resultado, lugar, fecha);
END |
delimiter |
CREATE FUNCTION calcularGanancia() RETURNS INT
BEGIN
DECLARE class, dinero INT;
SELECT
resultado, clasificacion
INTO class FROM
batalla
INNER JOIN
entrenador USING (idEntrenador)
WHERE
batalla.idEntrenador = entrenador.idEntrenador;
CASE class
WHEN 1 THEN SET dinero=250;
WHEN 2 THEN SET dinero=500;
WHEN 3 THEN SET dinero=1000;
WHEN 4 THEN SET dinero=2000;
ELSE SET dinero=0;
END CASE;
IF resultado = TRUE
THEN SET dinero = dinero * 1;
ELSE
SET dinero = dinero * -1;
END IF;
RETURN dinero;
END |
delimiter |
CREATE TRIGGER ricardoUpdate BEFORE
INSERT ON batalla
FOR EACH ROW BEGIN
UPDATE ricardo
SET perdidas=(SELECT COUNT(resultado) FROM batalla WHERE resultado=FALSE),
victorias=(SELECT COUNT(resultado) FROM batalla WHERE resultado=TRUE),
ganancias= ganancias + (SELECT CALCULARGANANCIA());
END |
I get this error with my function, Error Code 1222: The used SELECT statements have a different number of columns.

Answer 1

[edited]
That error usually means you have to explicitly pick the columns of your joined tables. Try changing your select in your calcularGanancia() function to something like the following (note I used aliases bat and ent):
declare class, resultado, dinero INT; /* note resultado here and into clause */
select bat.resultado, ent.clasificacion
into resultado, class
from batalla bat inner join
entrenador ent
ON bat.idEntrenador = ent.idEntrenador;