title: Can we Use Venn Diagrams to Characterise the Relationship between INNER, OUTER, LEFT and RIGHT JOINs?
body: <p>A related question &amp; answer (<a href="https://stackoverflow.com/questions/61685512/is-it-appropriate-to-use-venn-diagrams-to-depict-sql-joins-where-the-tables-are">Is It Appropriate to use Venn Diagrams to Depict SQL Joins where the Tables are Sets?</a>) demonstrate that it is inappropriate to characterise joins, in general, with the following Venn diagram:</p>
  
  <p><a href="https://i.stack.imgur.com/cQZCg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cQZCg.png" alt="enter image description here"></a></p>
  
  <p>However, my intuition still says that Venn diagrams can be useful to depict some relationships between inner/outer/left/right joins. Can this intuition be formalised? </p>