[ericHosick]

I would also like to know why you are getting downvoted.

Even wikipedia uses a Venn diagram to explain JOIN https://en.wikipedia.org/wiki/Join_(SQL) .

Not trying to use an argument from authority but just pointing out that this is not unheard of.

[radiospiel]

Venn diagrams are a terrible way to describe join types (and, tbh, I don’t understand why Wikipedia has these) because it makes it look like applying an 1:1 relationship. In a M:N relationship „artefacts“ (for lack of better words) of both tables would appear multiple times, and the venn diagram obscures this fact

[ericHosick]

> because it makes it look like applying an 1:1 relationship.

People can form different mental models of the same abstraction so I see what you are saying

I've never seen it that way because "Venn diagrams do not generally contain information on the relative or absolute sizes (cardinality) of sets." (see https://en.wikipedia.org/wiki/Venn_diagram).