updating column value based on another column value

Question

I'm working on Library Database and it contains a table called book_transaction. There are 2 columns called issued_date and due_date. due_date should be 7 days from issued_date. Can I specify this condition using default key word while creating the table?

If it is not possible please leave an alternative for the same.

Thank you,

Answer 1

Oracle default constraints cannot refer to other columns. You can get the same functionality using a trigger (see this answer):

CREATE TRIGGER book_transaction_trigger
  BEFORE INSERT ON book_transaction
  FOR EACH ROW
BEGIN
  IF :new.due_date IS NULL THEN
    :new.due_date := :new.issued_date + 7;
  END IF;
END book_transaction_trigger;

You can add days by adding a number to a date.

Answer 2

You can create a trigger for the table..

CREATE TRIGGER test_trigger BEFORE INSERT ON `book_transaction` 
FOR EACH ROW SET NEW.issued_date = IFNULL(NEW.entryDate,NOW()),
NEW.due_date = TIMESTAMPADD(DAY,7,NEW.issued_date)