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I am working on SQL Server 2008, and wanted to know about what is the differnce between Cartesian Product and Cross Join. Can somebody please help me to clear the concept?
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In SQL Server, the cartesian product is really a cross-join which returns all the rows in all the tables listed in a query: each row in the first table is paired with all the rows in the second table.
It's just the same symbol, and definitely not the same thing: the Cartesian product is a set (of vectors), the cross product is a vector.
The cross join produces the cross product or Cartesian product of two tables whereas the natural join is based on all the columns having the same name and data types in both the tables.
CROSS JOIN is simply Cartesian Product of two tables, irrespective of any filter criteria or any condition. FULL OUTER JOIN gives unique result set of LEFT OUTER JOIN and RIGHT OUTER JOIN of two tables. It also needs ON clause to map two columns of tables.
When you do Cross join you will get cartesian product. Each row in the first table is matched with every row in the second table
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This join is a Cartesian join that does not necessitate any condition to join. The resultset contains records that are multiplication of record number from both the tables.
/* CROSS JOIN */
SELECT t1.*,t2.*
FROM Table1 t1
CROSS JOIN Table2 t2
Sorce:
APRIL 13, 2009 BY PINAL DAVE
SQL SERVER – Introduction to JOINs – Basic of JOINs
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Both the joins give same result. Cross-join is SQL 99 join and Cartesian product is Oracle Proprietary join.
A cross-join that does not have a 'where' clause gives the Cartesian product. Cartesian product result-set contains the number of rows in the first table, multiplied by the number of rows in second table. (Resulting in a higher dimension in the resulting set).
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