Sql 使用编译错误创建的触发器

我编写此触发器是为了在进行新购买时将数据库中的顶级客户折扣10%：

CREATE or REPLACE TRIGGER CLIENT_DISCOUNT
  BEFORE INSERT
  ON PURCHASE
  FOR EACH ROW
DECLARE
  CLIENTNO  NUMBER(5);
BEGIN
  SELECT (SELECT CLIENT.CLIENTNO, CLIENT.CNAME, TOTALS.TOTAL FROM CLIENT, 
    (SELECT CLIENTNO, SUM(AMOUNT) AS TOTAL FROM PURCHASE GROUP BY CLIENTNO) TOTALS WHERE CLIENT.CLIENTNO = TOTALS.CLIENTNO  AND ROWNUM <= 1 ORDER BY TOTALS.TOTAL DESC).CLIENTNO INTO CLIENTNO;
  IF :NEW.CLIENTNO = CLIENTNO THEN
    :NEW.AMOUNT = (:NEW.AMOUNT * 0.1);
  END IF;
END;

有人能告诉我我做错了什么吗

谢谢， 亚历克斯

更新-错误：

Errors for TRIGGER CLIENT_DISCOUNT:

LINE/COL
--------------------------------------------------------------------------------
ERROR
--------------------------------------------------------------------------------
4/3
PL/SQL: SQL Statement ignored

5/141
PL/SQL: ORA-00907: missing right parenthesis

7/17
PLS-00103: Encountered the symbol "=" when expecting one of the following:


LINE/COL
--------------------------------------------------------------------------------
ERROR
--------------------------------------------------------------------------------
   := . ( @ % ; indicator

8/3
PLS-00103: Encountered the symbol "END"

解决方案：

CREATE or REPLACE TRIGGER CLIENT_DISCOUNT
    BEFORE INSERT
    ON PURCHASE
    FOR EACH ROW
DECLARE
    vCLIENTNO  NUMBER(5);
BEGIN
    SELECT TOPCLIENT.CLIENTNO INTO vCLIENTNO FROM (SELECT CLIENT.CLIENTNO, CLIENT.CNAME, TOTALS.TOTAL FROM CLIENT, (SELECT CLIENTNO, SUM(AMOUNT) AS TOTAL FROM PURCHASE GROUP BY CLIENTNO) TOTALS WHERE CLIENT.CLIENTNO = TOTALS.CLIENTNO  AND ROWNUM <= 1 ORDER BY TOTALS.TOTAL DESC) TOPCLIENT;
    IF :NEW.CLIENTNO = vCLIENTNO THEN
        :NEW.AMOUNT := (:NEW.AMOUNT * 0.9);
    END IF;
END;
/

试一试

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我手头没有你的桌子，所以我不能保证我发现了你所有的错误。不过，我可以说：

我不相信你能做选择…客户不。请尝试从…中选择x.CLIENTNO。。。。而是x。 最外层的SELECT没有FROM子句。尝试从DUAL添加，因为此最外层的SELECT不是从任何表中选择的。 PL/SQL赋值运算符为：=，而不是=。要分配给：NEW.AMOUNT，您需要写入：NEW.AMOUNT:=：NEW.AMOUNT*0.1；。 将金额乘以0.1，客户可以享受90%的折扣，而不是10%的折扣。

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除了其他人识别的语法错误外，很可能是由于无法从插入的表中进行选择而导致触发器发生变化

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如果可以更改数据模型，则可能需要在另一个表中标识顶级客户机，而不是在插入到该表中时尝试选择金额总和购买表

问题显示错误描述列表。我添加了SealError Salx的输出，您可能需要考虑命名您的本地变量与您的SQL查询中的表列不同。也许用v_u前缀表示变量，或用l_u前缀表示局部变量。在我看来有点混乱，如果顶级客户频繁更改会发生什么，您如何知道折扣已正确应用。这只是一个学习练习，我遇到了麻烦，因此它不会用于任何生产系统。

CREATE or REPLACE TRIGGER CLIENT_DISCOUNT
    BEFORE INSERT
    ON PURCHASE
    FOR EACH ROW
DECLARE
    vCLIENTNO  NUMBER(5);
BEGIN
    SELECT TOPCLIENT.CLIENTNO INTO vCLIENTNO FROM (SELECT CLIENT.CLIENTNO, CLIENT.CNAME, TOTALS.TOTAL FROM CLIENT, (SELECT CLIENTNO, SUM(AMOUNT) AS TOTAL FROM PURCHASE GROUP BY CLIENTNO) TOTALS WHERE CLIENT.CLIENTNO = TOTALS.CLIENTNO  AND ROWNUM <= 1 ORDER BY TOTALS.TOTAL DESC) TOPCLIENT;
    IF :NEW.CLIENTNO = vCLIENTNO THEN
        :NEW.AMOUNT := (:NEW.AMOUNT * 0.9);
    END IF;
END;
/

CREATE or REPLACE TRIGGER CLIENT_DISCOUNT
  BEFORE INSERT
  ON PURCHASE
  FOR EACH ROW
DECLARE
  vCLIENTNO  NUMBER(5);
BEGIN
  SELECT Z.CLIENTNO INTO vCLIENTNO FROM (SELECT CLIENT.CLIENTNO, CLIENT.CNAME, TOTALS.TOTAL FROM CLIENT, 
    (SELECT CLIENTNO, SUM(AMOUNT) AS TOTAL FROM PURCHASE GROUP BY CLIENTNO) TOTALS WHERE CLIENT.CLIENTNO = TOTALS.CLIENTNO  AND ROWNUM <= 1 ORDER BY TOTALS.TOTAL DESC) Z;
  IF :NEW.CLIENTNO = vCLIENTNO THEN
    :NEW.AMOUNT := (:NEW.AMOUNT * 1.091);
  END IF;
END;