How to make use of variable on a function

Question

I need to make a stored function:

This is my code

SELECT count(Dominio) FROM Thogar WHERE DOMINIO='%'

I need to make a stored function where I will write a letter between (U,C,R) and the function will replace the % in the previous code with the selected letter.

How can I do it? Thanks!

Got it working

CREATE FUNCTION `Buscar`(`param` CHAR(1))
    RETURNS INT
    LANGUAGE SQL
    NOT DETERMINISTIC
    CONTAINS SQL
    SQL SECURITY DEFINER
    COMMENT ''
BEGIN
    DECLARE res INT;
    SELECT count(Dominio) INTO res FROM Thogar WHERE DOMINIO=param;
    RETURN res;
END

    Call buscar('C')

Answer 1

This should work:

DROP FUNCTION IF EXISTS myFunc;
DELIMITER $$
CREATE FUNCTION myFunc(
    param CHAR(1)
) RETURNS INT;
BEGIN
    DECLARE res INT;
    SELECT count(Dominio) INTO res FROM Thogar WHERE DOMINIO=param;
    RETURN res;
END;
$$
DELIMITER ;