1
The JOIN operation combines tuples from two relations into a single relation based on a specific join condition. It is equivalent to a Cartesian product followed by a selection operation.
2
A THETA Join allows relations to be joined using comparison operators other than equality, such as less than, greater than, or not equal to (represented by theta).
3
An EQUIJOIN is a specific type of join where the comparison operator in the join condition is strictly equality.
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A NATURAL JOIN is an equi-join that automatically eliminates duplicate columns by matching common attributes between two relations with the same name.
5
The DIVISION operation is used in queries that involve the keyword 'all' (e.g., finding employees who work on all projects), and can be derived using projection, cross product, and set difference operations.