问题描述
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,)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;
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 表上创建一个触发器，它会告诉我操作成本是多少。
为了得到这个信息，当一个操作插入到表中时，我想检查操作的类型，然后进入合约的tariff_plan找到操作的价格。
我尝试过：
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？
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;
/
解决方法
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,'CALL',v_tariff_plan.call_price );
ELSE
INSERT INTO log_what_happened ( id,'CONTRACT',NULL );
END IF;
END;
/
如果你有桌子：
CREATE TABLE log_what_happened (
id INTEGER,type VARCHAR2(20),price DECIMAL(3,2)
);
并将数据插入到您的表格中：
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,'777' ) FROM DUAL;
那么：
SELECT * FROM log_what_happened;
输出：
ID | TYPE | PRICE -: | :------- | ----: 1 | CALL | .1 2 | CONTRACT | null 3 | SMS | .01
dbfiddle here