Alright! Let's summarize everything we learned in this part.

• We don't have to join tables on the primary-foreign key relationship. It is possible to use any two columns:

  SELECT
    Buyer.Name,
    Car.Name
  FROM Buyer
  JOIN Car
    ON Owner.PreferredCarType = Car.Type
  

  The query above will show the name of every buyer together with every car that matches their preferred type.
• We also don't have to use the equality operator when joining tables. We are free to use other comparison operators (<, >, <=, >=, !=, <>) or the BETWEEN operator:

  SELECT
    Auctioneer.Name,
    Item.Name
  FROM Auctioneer
  JOIN Item
    ON Auctioneer.Funds > Item.Price
  

• We can write a special kind of JOIN to list items within a certain range (for example, within a budget), all pairs of items, or all unique pairs.