我想用mysql生成一个类似“b45”的代码。生成从'a0'开始，以'y99'结束，但不知怎么的，有一个问题，请我需要帮助我的代码

CREATE TRIGGER oeuvre_code BEFORE INSERT ON oeuvres
    BEGIN
        IF NOT EXISTS(select * from oeuvres) THEN
            SET @code2 ='A0';
        ELSE
            SET @test = (select code from oeuvres LIMIT 1);
            SET @char =(select left (@test,1));
            SET @nbr = select substr(@test,2);
            if @char!='Z' AND @nbr+0 <99 THEN
                set @char2 = select (ASCII(@char)+1);
                set @nbr2 = @nbr+1;</i>

            END IF;
            set @code2=@char2+@nbr2;
            INSERT INTO oeuvres VALUES(NEW.Id,NEW.Toile,NEW.Description,NEW.Prix,NEW.Date,NEW.Etat,@code2);
        END IF;
    END;

问题是：

Error
SQL query: Documentation

CREATE TRIGGER oeuvre_code BEFORE INSERT ON oeuvres
    BEGIN
        IF NOT EXISTS(select * from oeuvres) THEN
            SET @code2 ='A0'
MySQL said: Documentation

# 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'BEGIN

        IF NOT EXISTS(select * from oeuvres) THEN
            SET @code2' at line 2

我得到的问题的图片