Amazing! Let's summarize what we have learned. You know how to ...

• ... use INSERT INTO with SELECT to insert data from one table into another:

  INSERT INTO history_purchase
  SELECT * FROM purchase;

• ... delete information from one table based on data from another table, as in DELETE FROM ... USING:

  DELETE FROM purchase
  USING product
  WHERE product.id = purchase.product_id
    AND product.price IS NULL;

• ... update data in one table based on data from another table by using UPDATE ... FROM:

  UPDATE purchase
  SET
    purchase.total_price = product.price * purchase.quantity
  FROM product
  WHERE purchase.product_id = product.id;

• ... write INSERT, UPDATE, and DELETE statements that include subqueries:

  DELETE FROM product
  WHERE id NOT IN (SELECT product_id FROM purchase)
    AND delivered_timestamp < CURRENT_TIMESTAMP - INTERVAL '3 years';

Note: INSERT, UPDATE, and DELETE operations can also include common table expressions (CTEs). However, an explanation of that is beyond the scope of this course. If you would like to learn more about it, check out our Recursive Queries in PostgreSQL course.