Oracle Trigger Typical Examples

• Sync table A to Table B

CREATE TABLE A(ID INT,DESCRIPTION VARCHAR(10));
CREATE TABLE B(ID INT,DESCRIPTION VARCHAR(10));

CREATE OR REPLACE TRIGGER SYNC_A_TO_B AFTER INSERT OR UPDATE OR DELETE ON A FOR EACH ROW --indicate that this is a row trigger,not table level trigger BEGIN DBMS_OUTPUT.PUT_LINE(:NEW.ID || '-' || :NEW.DESCRIPTION);
  DBMS_OUTPUT.PUT_LINE(:OLD.ID || '-' || :OLD.DESCRIPTION);
  CASE
    WHEN INSERTING THEN 
      DBMS_OUTPUT.PUT_LINE('INSERTING');
      INSERT INTO B VALUES (:NEW.ID,:NEW.DESCRIPTION);
    WHEN UPDATING THEN
      DBMS_OUTPUT.PUT_LINE('UPDATING');
      UPDATE B SET B.DESCRIPTION = :NEW.DESCRIPTION WHERE B.ID = :NEW.ID;
    WHEN DELETING THEN
      DBMS_OUTPUT.PUT_LINE('DELETING');
      DELETE FROM B WHERE B.ID = :OLD.ID;
  END CASE;
END;
/

INSERT INTO A VALUES (1,'A_TO_B');

SELECT * FROM A;
SELECT * FROM B;

UPDATE A SET A.DESCRIPTION = 'UPDATED' WHERE A.ID = 1;

SELECT * FROM A;
SELECT * FROM B;

DELETE FROM A WHERE A.ID = 1;

SELECT * FROM A;
SELECT * FROM B;

DROP TABLE A;
DROP TABLE B;

（编辑：李大同）

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