Really? Even if it NEVER produces the right answer? How is it useful then? A [inner|left|right|outer|cross|natural|whatever] join B NEVER produces a result t

Really? Even if it NEVER produces the right answer? How is it useful then? A [inner|left|right|outer|cross|natural|whatever] join B NEVER produces a result that is in either A or B. It produces something larger, that wasn't it A or B before. It's like trying to describe the result of meiosis with a Venn diagram. It's the combinations that matter, and the combinations are not reflected in the Venn diagram.