如何知道触发器中 :new 的类型？

Question

假设我有这些虚拟类型和这些类型的表：

create or replace type Tariff_Plan_TY as object(
  tariff_id INTEGER,
  call_price DECIMAL(3,2),
  sms_price DECIMAL(3,2),
)FINAL;

create or replace type Contract_TY as object(
  telephone_no VARCHAR(10),
  tariff_plan REF Tariff_Plan_TY
)NOT FINAL;

create or replace
type Operation_TY as object(
  id INTEGER,
  contract REF Contract_TY
)NOT FINAL;

我们还假设我有不同类型的操作：

create or replace type Call_TY UNDER Operation_TY(
  called_no VARCHAR(10),
  end_time TIMESTAMP WITH LOCAL TIME ZONE
)FINAL;

create or replace type SMS_TY UNDER Operation_TY(
  receiver_no VARCHAR(10)
)FINAL;

我想在Operation_TY 的表上创建一个触发器，它会告诉我操作成本是多少。 为了得到这些信息，当一个操作被插入到表中时，我想检查该操作的类型，然后进入合约的tariff_plan 找到该操作的价格。

我试过了：

create or replace
TRIGGER CHECK_OPERATION
BEFORE INSERT ON OPERATION_TB
FOR EACH ROW
DECLARE
  contract contract_ty;
  tariff_plan tariff_plan_ty;
  operation ref operation_ty;
BEGIN
  operation = ref :new;
  SELECT deref(:new.contract) into contract from dual;
  SELECT deref(contract.tariff_plan) into tariff_plan from dual;

  if (operation is of (sms_ty)) then
    NULL; -- go search the price
  elsif (operation is of (call_ty)) then
    NULL; -- go search the price
  else
    NULL;
  end if;
END;

这不起作用，我想我错过了一些东西。这个操作应该如何进行？

我在这里留下一个小脚本来随机填充表格：

create table Contract_TB of Contract_TY;
/
create table Tariff_Plan_TB of Tariff_Plan_TY;
/
create table Operation_TB of Operation_TY;
/
create or replace PROCEDURE POPULATE_TARIFF_PLAN AS
idx INTEGER;  
BEGIN 
  idx := 0;
  LOOP 
    INSERT INTO tariff_plan_tb
    VALUES (
      idx,
      DBMS_RANDOM.VALUE,
      DBMS_RANDOM.VALUE
      ); 
  idx := idx + 1;
  EXIT WHEN idx = 10;
  end loop;
END POPULATE_TARIFF_PLAN;
/
create or replace
PROCEDURE populate_contract AS
idx INTEGER;
phone_no VARCHAR(10);
ref_tariff_plan REF Tariff_Plan_TY;
BEGIN
  idx := 0;
  SELECT TO_CHAR(
    TRUNC(DBMS_RANDOM.VALUE(1000000000, 9999999999))
  ) INTO phone_no FROM DUAL;

  SELECT * INTO ref_tariff_plan FROM(
    SELECT REF(T)
    FROM tariff_plan_tb T
    ORDER BY DBMS_RANDOM.VALUE
  ) WHERE rownum <= 1;

  INSERT INTO contract_tb
  VALUES (phone_no,
        ref_tariff_plan);
  idx := idx + 1;
  EXIT WHEN idx = 500;
  END LOOP;
END;
/

create or replace
procedure populate_operation as
idx NUMBER;
ref_contract ref Contract_TY;
begin
idx := 0;
loop 
  SELECT * into ref_contract FROM(SELECT ref(ct) FROM CONTRACT_TB ct ORDER BY dbms_random.value) WHERE rownum <= 1;
  INSERT INTO OPERATION_TB values(
      SMS_TY(
        idx,
        ref_contract
      ));
      idx := idx + 1;
    exit when idx = 1000;
end loop;
end;
/

Answer 1

使用OBJECT_VALUE pseudo-column 获取行对象。

CREATE TRIGGER CHECK_OPERATION
BEFORE INSERT ON OPERATION_TB
FOR EACH ROW
DECLARE
  v_contract    contract_ty;
  v_tariff_plan tariff_plan_ty;
BEGIN
  SELECT DEREF( :NEW.contract )
  INTO   v_contract
  FROM   DUAL;

  SELECT DEREF( v_contract.tariff_plan )
  INTO   v_tariff_plan
  FROM   DUAL;

  IF :NEW.OBJECT_VALUE IS OF ( SMS_TY ) THEN
    INSERT INTO log_what_happened ( id, type, price )
      VALUES ( :NEW.ID, 'SMS', v_tariff_plan.sms_price );
  ELSIF :NEW.OBJECT_VALUE IS OF ( CALL_TY ) THEN
    INSERT INTO log_what_happened ( id, type, price )
      VALUES ( :NEW.ID, 'CALL', v_tariff_plan.call_price );
  ELSE
    INSERT INTO log_what_happened ( id, type, price )
      VALUES ( :NEW.ID, 'CONTRACT', NULL );
  END IF;
END;
/

如果你有桌子的话：

CREATE TABLE log_what_happened (
  id    INTEGER,
  type  VARCHAR2(20),
  price DECIMAL(3,2)
);

并将数据插入您的表中：

INSERT INTO Tariff_Plan_TB
SELECT 1, 0.10, 0.01 FROM DUAL UNION ALL
SELECT 2, 0.20, 0.02 FROM DUAL;

INSERT INTO Contract_TB
SELECT '1', ( SELECT REF(t) FROM Tariff_Plan_TB t WHERE tariff_id = 1 ) FROM DUAL UNION ALL
SELECT '2', ( SELECT REF(t) FROM Tariff_Plan_TB t WHERE tariff_id = 2 ) FROM DUAL;

INSERT INTO Operation_TB
SELECT Call_TY( 1, ( SELECT REF(c) FROM Contract_TB c WHERE telephone_no = '1' ), '555', SYSTIMESTAMP ) FROM DUAL UNION ALL
SELECT OPERATION_TY( 2, ( SELECT REF(c) FROM Contract_TB c WHERE telephone_no = '2' ) ) FROM DUAL UNION ALL
SELECT SMS_TY( 3, ( SELECT REF(c) FROM Contract_TB c WHERE telephone_no = '1' ), '777' ) FROM DUAL;

然后：

SELECT * FROM log_what_happened;

输出：

身份证 |类型 |价钱 -: | :------- | ----: 1 |电话 | .1 2 |合同 | 空 3 |短信 | .01

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