What is the correct way to implement controlled Primary key depending on column values - product classifications tree

问题

I am trying to make Table Product_Classification to Classify Products on three levels columns as below

I think it is something called table with it self relation

CREATE TABLE Product_Classification
(
   Classification_ID   NUMBER           NOT NULL,
   Classification_Desc VARCHAR2 (1024)  NOT NULL,
   Class1_ID           NUMBER,
   Class1_Desc         VARCHAR2 (1024),
   Class2_ID           NUMBER,
   Class2_Desc         VARCHAR2 (1024),
   Class3_ID           NUMBER,
   Class3_Desc         VARCHAR2 (1024),
   Notes               VARCHAR2 (1024),
   Created_By          VARCHAR2 (64)    NOT NULL,
   Created_On          DATE             NOT NULL,
   Updated_By          VARCHAR2 (64),
   Updated_On          DATE,
   --------------------Constraint--------------------
   CONSTRAINT PK_Classification_ID PRIMARY KEY (Classification_ID)
);
/

Classification_ID it should be controlled Primary key which will be the concatenation of Class1_ID, Class2_ID, and Class3_ID so each four digits in the primary key will allow me to access a level on the product classifications tree for example

Classification_ID  |    Classification_Desc |   class1_ID  |    class1_desc |   class2_ID | class2_desc   |  class3_ID| class3_desc
1000           |    example         |          |            |         |           |       |
10001111       |    example         |   1111       |    x product   |         |           |       |
100011112222       |    example         |   1111       |    x product   |   2222      | Product       |       |
1002           |    example1        |          |            |         |           |       |
10022222       |    example1        |   2222       |    y prodcut   |         |           |       | 
100222223333       |    example1        |   2222       |    y prodcut   |   3333      |     Product 1     |       |

So have created three sequences as below

CREATE SEQUENCE Seq_Classification_ID MINVALUE 1000
                                      MAXVALUE 999999999999999999      /* 18 Digits */
                                      START WITH 1000
                                      INCREMENT BY 1
                                      CACHE 20;
/   
CREATE SEQUENCE Seq_Class1_ID MINVALUE 1000
                              MAXVALUE 999999999999999999      /* 18 Digits */
                              START WITH 1000
                              INCREMENT BY 1
                              CACHE 20;
/
CREATE SEQUENCE Seq_Class2_ID MINVALUE 1000
                              MAXVALUE 999999999999999999      /* 18 Digits */
                              START WITH 1000
                              INCREMENT BY 1
                              CACHE 20;
/
CREATE SEQUENCE Seq_Class3_ID MINVALUE 1000
                              MAXVALUE 999999999999999999      /* 18 Digits */
                              START WITH 1000
                              INCREMENT BY 1
                              CACHE 20;
/

Now I tried to do that by using trigger as below

CREATE OR REPLACE TRIGGER Trg_Classification_ID_Seq
   BEFORE INSERT
   ON Product_Classification
   FOR EACH ROW
BEGIN

   IF (:NEW.CLASSIFICATION_DESC IS NOT NULL) THEN 
             :NEW.CLASSIFICATION_ID := :OLD.CLASSIFICATION_ID||:NEW.CLASS1_ID||:NEW.CLASS2_ID||:NEW.CLASS3_ID;
   ELSIF (:NEW.CLASSIFICATION_DESC IS NULL) THEN 
             :NEW.CLASSIFICATION_ID:=Seq_Classification_ID.NEXTVAL;        
   END IF;

   IF (:NEW.CLASS1_DESC IS NOT NULL) THEN
          :NEW.CLASS1_ID := Seq_Class1_ID.NEXTVAL;
   ELSIF (:NEW.CLASS1_DESC IS NULL) THEN
             :NEW.CLASS1_ID := NULL;
   END IF;

   IF (:NEW.CLASS2_DESC IS NOT NULL) THEN
             :NEW.CLASS2_ID := Seq_Class2_ID.NEXTVAL;
   ELSIF (:NEW.CLASS2_DESC IS NULL) THEN
             :NEW.CLASS2_ID := NULL;
   END IF;

   IF (:NEW.CLASS3_DESC IS NOT NULL) THEN
             :NEW.CLASS3_ID := Seq_Class3_ID.NEXTVAL;
   ELSIF (:NEW.CLASS3_DESC IS NULL) THEN
             :NEW.CLASS3_ID:=NULL;
   END IF;

END;

My problem is that I am getting cannot insert null value in CLASSIFICATION_ID

Second I do not know if that is the correct way to do something like that ?

I have also made a function to do that but that not correct way since I can insert record in table and the function will not be executed so I choose to use triggers which will be executed before each insert

please advice suggested

Thank all in advance

来源：https://stackoverflow.com/questions/42704445/what-is-the-correct-way-to-implement-controlled-primary-key-depending-on-column

标签

Oracle

oracle12c