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Oracle: What is a Cartesian product?

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Oracle: What is a Cartesian product?
posted Mar 9, 2015 by Suchithra

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2 Answers

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A cartesian product is a result from a select statement that returns all the data from both the tables . The result of a cartesian product is due to the unspecifying the where clause for the join select statement.

answer Mar 10, 2015 by Arun Gowda
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'If two tables in a join query have no join condition, then Oracle returns their Cartesian product. Oracle combines each row of one table with each row of the other.
A Cartesian product always generates many rows and is rarely useful.

For example, the Cartesian product of two tables, each with 100 rows, has 10,000 rows. Always include a join condition unless you specifically need a Cartesian product. If a query joins three or more tables and you do not specify a join condition for a specific pair, then the optimizer may choose a join order that avoids producing an
intermediate Cartesian product.'

answer Mar 9, 2015 by Amit Kumar Pandey
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