Difference between a theta join, equijoin and natural join

Question

I\'m having trouble understanding relational algebra when it comes to theta joins, equijoins and natural joins. Could someone please help me better understand it? If I use t

Answer 1

Natural is a subset of Equi which is a subset of Theta.

If I use the = sign on a theta join is it exactly the same as just using a natural join???

Not necessarily, but it would be an Equi. Natural means you are matching on all similarly named columns, Equi just means you are using '=' exclusively (and not 'less than', like, etc)

This is pure academia though, you could work with relational databases for years and never hear anyone use these terms.