Practice mode DBMS and SQL

Which of these relational algebra operations is not one of the basic operations, because it can be expressed using a Cartesian product followed by a selection and projection?

Correct answer A. Natural join

Explanation

The basic operations are selection, projection, union, set difference and Cartesian product (with rename). Join is a derived operation: a natural join equals a Cartesian product, a selection that equates the common attributes, and a projection removing duplicate columns. Set difference cannot be built from the others, so it is basic. Join is still provided directly because it is so common and can be implemented efficiently.

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Which of these relational algebra operations is not one of the basic operations, because it can be expressed using a Cartesian product followed by a selection and projection?

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Which of these relational algebra operations is not one of the basic operations, because it can be expressed using a Cartesian product followed by a selection and projection?

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