触发器中的另一个错误绑定变量

Question

得到一个错误的绑定变量“old.seatsremain”和“new.seatsremain”。如果席位可用于特定产品，则尝试使此触发器自动减少产品的席位数量。我是否必须在前面声明所有变量：？？？？我的两张桌子是：

enrollments
{sid number,
offerno number;)

和

offering
{offerno number,
courseno varchar2(10),
instructor varchar2(10),
seatsremain number;}

更新的代码测试： 好的，所以我合并了 Fumble 给我的编码，它清除了最初弹出的错误，但是我测试了这个新代码，我仍然有一些剩余的错误，因为我不知道为什么的 EXCEPTION 子句，因为我仔细检查的语法应该是正确的。有什么想法吗？？

create or replace trigger enroll_bef_ins_row
before insert on enrollments
for each row
declare
    originstruct    offering.instructor%type;
    origcourseno    offering.courseno%type;
    original    offering.seatsremain%type;
    seatsremain_already_full    exception;
begin
    Select seatsremain, instructor, courseno into original, originstruct, origcourseno from offering where offerno= :new.offerno;
    if original > 0 then
        update offering set seatsremain= seatsremain - 1;
        dbms_output.put_line ('Seats available in offering'||offerno||'have decreased from'||original|| 'to' ||(seatsremain));
    else if original = 0 then
        raise seatsremain_already_full;
        dbms_output.put_line ('Offering'||offerno||'is already full!');
    else
        update offering set offerno = :old.offerno;
        update offering set courseno = origcourseno;
        update offering set instructor = originstruct;
        update offering set seatsremain = original;

    end if;

exception
    when seatsremain_already_full then
        raise_application_error (-20001, 'Cannot allow insertion');
commit;
end;
/

现在出现此错误： PLS-00103：在期待一个时遇到符号“例外” 以下的： 开始 case 声明 goto 的结束退出 if loop mod null pragma 在使用时提高返回选择更新

PLS-00103：预期时遇到符号“文件结尾” 以下之一： end not pragma final 可实例化顺序覆盖静态

Answer 1

您正在使用表中的相关名称，而不是为其创建触发器的表。尝试将 oldSeatsRemain 和 NewSeatsRemain 声明为触发器中的变量。

试试这个（注意：这个示例尚未执行）。它包括我在 cmets 中描述的编辑。

    create or replace trigger enroll_bef_ins_row
    before insert on enrollments
    for each row

    declare
        offerrow offering%rowtype;
        seatsremain_already_full    exception;
        pragma autonomus_transaction;
    begin
        Select seatsremain into offerrow from offering where offerno= :new.offerno;
        if offerrow.seatsremain > 0 then
            update offering set seatsremain= offerrow.seatsremain - 1;
            dmbs_output.put_line ('Seats available in offering ' |offerno| ' have decreased from ' |offerrow.seatsremain| ' to ' |offerrow.seatsremain-1|);
        else if original = 0 then
            dbms_output.put_line ('Offering ' |offerno| ' is already full!');
            raise seatsremain_already_full;
        else
            insert into offering
            values(offering.offerno,offering.courseno,offering.instructor,offering.seatsremain);
        end if;
        commit;
    exception
        when seatsremain_already_full
        raise_application_error (-20001, 'Cannot allow insertion');
    end
    /