January 2019
Beginner
556 pages
14h 19m
English
Content preview from Learning PostgreSQL 11 - Third Edition
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The Cartesian product operation
The Cartesian product operation is used to combine tuples from two relations into a single one. The number of attributes in the single relation equals the sum of the number of attributes of the two relations. The number of tuples in the single relation equals the product of the number of tuples in the two relations. Let's assume that A and B are two relations, and C = A × B:
The number of attributes of C = the number of attributes of A + the number of attributes of B
The number of tuples of C = the number of tuples of A * the number of tuples of B
The following table shows the cross join of customer and customer service:
The equivalent SQL join for Cartesian product is CROSS JOIN; the query for the customer ...
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