sql自定义函数报错～求指导

Question

为什么这个函数会返回多个值？

DELIMITER $$
create function check_or_alter_pwd(name VARCHAR(255),pwd VARCHAR(255),newpwd VARCHAR(255),act INT) returns boolean
begin
    declare pawd VARCHAR(255);
    SELECT passwd INTO @pawd FROM acount WHERE user_name = name;
    IF @pawd IS NULL OR @pawd != pwd THEN
        SELECT 'Invalid username or password';
        return False;
    end if;
    IF act = 1 THEN
        SELECT 'Login successful';
        return True;
    ELSEIF act = 2 THEN        
        IF CHAR_LENGTH(newpwd) < 4 OR CHAR_LENGTH(newpwd) > 10 OR NOT(newpwd REGEXP '^[a-zA-Z0-9]+$') THEN
            SELECT 'Invalid new password';
            return False;
        else 
            UPDATE acount SET passwd = newpwd WHERE user_name = name;
            SELECT 'Password changed successfully';
            return True;  
        end if;
    ELSE
        SELECT 'Invalid action';
        return False;
    END IF;
end $$
DELIMITER ;

报错是这个

Answer 1

把所有的select 字符串注释掉