Great! We've reached the final section for this part. Let's review what we've learned.

A database architect can define a default value for a column. You can use DEFAULTs ...

• ... in an INSERT statement:

  INSERT INTO author (id, first_name, last_name, photo, create_timestamp, is_active) VALUES
  (120, 'Gary', 'Brown', 'imgs/gary.jpg', '2018-08-25', DEFAULT);

• ... by omitting columns in INSERT:

  INSERT INTO author (id, first_name, last_name) VALUES
  (121, 'Mary', 'Taylor');

• ... during an UPDATE operation:

  UPDATE author
    photo = DEFAULT
  WHERE id = 120;

Plus, you learned how to auto-generate unique values by:

• Using SERIAL and omitting the name of the ID column:

  INSERT INTO author(first_name, last_name) VALUES
  ('Stanley', 'Lewis');

• Using DEFAULT to generate a SERIAL value:

  INSERT INTO author VALUES
  (DEFAULT, 'Mark', 'Barker', 'imgs/barker1.jpg', DEFAULT, DEFAULT);

• Using a sequence:

  INSERT INTO author (id, first_name, last_name, is_active) VALUES
  (NEXTVAL('id_seq',  'Miriam', 'Clerk', 1);

Remember, auto-generated values from the same sequence can be used in multiple tables and each value will be unique.