The join operation is derived from the Cartesian product operation of relational algebra. We can
say join operation is a combination of the operations selection, projection and Cartesian product.
There are various forms of join operation such as theta join, equi join, natural join, outer join and
semijoin. The outer join operation is further classifi ed into full outer join, left outer join and right
outer join.
(i)Theta join (θ) – The most common join operation is theta join. The theta join operation of two
relations R and S defi nes a relation that contains tuples satisfying a join predicate ...
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