无法从现有列中填充 table 中的新列

Question

我有车table。它的结构如下：

CREATE TABLE cars ( 
  ID NUMBER(38) PRIMARY KEY,
  Manufacturer VARCHAR2(26),
  Model VARCHAR2(26),
  Year NUMBER(38),
  Category VARCHAR2(26),
  Mileage NUMBER(38),
  FuelType VARCHAR2(26),
  EngineVolume VARCHAR2(26),
  DriveWheels VARCHAR2(26),
  GearBox VARCHAR2(26),
  Doors VARCHAR2(26),
  Wheel VARCHAR2(26),
  Color VARCHAR2(26),
  InteriorColor VARCHAR2(26),
  VIN VARCHAR2(26),
  LeatherInterior VARCHAR2(26),
  Price NUMBER(38),
  Clearance VARCHAR2(26),
  Age NUMBER(38),
  PriceInTg NUMBER(38)
 )

我想填充从其他列填充的 age 和 'PriceInTg' 列。所以我为它创建了填充函数：

CREATE OR REPLACE FUNCTION age_converter(Year NUMBER) 
RETURN NUMBER
IS
v_age Number;
BEGIN
    v_age := EXTRACT(YEAR FROM SYSDATE) - Year;
    RETURN v_age;
END;


CREATE OR REPLACE FUNCTION price_converter(Price NUMBER, currency_in_tg NUMBER)
RETURN NUMBER
IS
price_in_tg NUMBER;
BEGIN 
    price_in_tg := Price  * currency_in_tg;
    RETURN price_in_tg;
END;

为了自动填充这些列，我创建了触发器：

CREATE OR REPLACE TRIGGER age_filler_trigger
AFTER INSERT ON cars FOR EACH ROW
BEGIN
    INSERT INTO cars (age)
    VALUES (age_converter(:OLD.year));
END;

CREATE OR REPLACE TRIGGER priceTg_filler 
AFTER INSERT ON cars FOR EACH ROW
BEGIN
    INSERT INTO cars (age)
    VALUES (price_converter(:OLD.price, 430));
END;

但是当我像这样向 table 插入值时：

 INSERT INTO CARS (ID, MANUFACTURER, MODEL, YEAR, CATEGORY, MILEAGE, FUELTYPE, ENGINEVOLUME, DRIVEWHEELS, GEARBOX, DOORS, WHEEL, COLOR, INTERIORCOLOR, VIN, LEATHERINTERIOR, PRICE, CLEARANCE)
 VALUES (0,'BMW','M6',2014,'Coupe',33500,'Petrol','4.4','Rear','Tiptronic','4/5','Left wheel','White','Black','','true',39000,'false');

我遇到了这样的错误：

Error starting at line : 6 in command -
INSERT INTO CARS (ID, MANUFACTURER, MODEL, YEAR, CATEGORY, MILEAGE, FUELTYPE, ENGINEVOLUME, DRIVEWHEELS, GEARBOX, DOORS, WHEEL, COLOR, INTERIORCOLOR, VIN, LEATHERINTERIOR, PRICE, CLEARANCE) VALUES (0,'BMW','M6',2014,'Coupe',33500,'Petrol','4.4','Rear','Tiptronic','4/5','Left wheel','White','Black','','true',39000,'false')
Error report -
ORA-04091: table PROJECT.CARS is mutating, trigger/function may not see it
ORA-06512: at "PROJECT.PRICETG_FILLER", line 2
ORA-04088: error during execution of trigger 'PROJECT.PRICETG_FILLER'

我该如何处理这个问题？

Answer 1

您的插入触发器不应尝试插入新行。相反，他们应该设置 :new 值，例如

:NEW.year := age_converter(:OLD.year);

我本来打算同时创建 AGE 和 PRICE 虚拟列，但它们不能使用 sysdate，因此即时计算年龄是个问题。但这无论如何都是一个问题，因为您设置的任何值都只会反映该行最后一次更新时的年龄，这可能是过去的任何时间，因此永远不会可靠。最好在 cars table 上创建一个视图，因为这样您就可以包含一个反映查询时间的 AGE 列。

“tg 价格”列可以是虚拟的：

priceintg number(38) generated always as (price * 430)

无法从现有列中填充 table 中的新列

Failed to fill new columns in table from existing ones

oracle

triggers

plsql