Using Cross Joins
A cross join that does not have a WHERE clause produces the Cartesian product of the tables involved in the join. The size of a Cartesian product result set is the number of rows in the first table multiplied by the number of rows in the second table. The following example shows a Transact-SQL cross join.
USE AdventureWorks;
GO
SELECT p.SalesPersonID, t.Name AS Territory
FROM Sales.SalesPerson p
CROSS JOIN Sales.SalesTerritory t
ORDER BY p.SalesPersonID;
The result set contains 170 rows (SalesPerson has 17 rows and SalesTerritory has 10; 17 multiplied by 10 equals 170).
However, if a WHERE clause is added, the cross join behaves as an inner join. For example, the following Transact-SQL queries produce the same result set.
USE AdventureWorks;
GO
SELECT p.SalesPersonID, t.Name AS Territory
FROM Sales.SalesPerson p
CROSS JOIN Sales.SalesTerritory t
WHERE p.TerritoryID = t.TerritoryID
ORDER BY p.SalesPersonID;
-- Or
USE AdventureWorks;
GO
SELECT p.SalesPersonID, t.Name AS Territory
FROM Sales.SalesPerson p
INNER JOIN Sales.SalesTerritory t
ON p.TerritoryID = t.TerritoryID
ORDER BY p.SalesPersonID;
See Also
Concepts
Using Operators in Expressions
Other Resources
WHERE (Transact-SQL)
SELECT (Transact-SQL)
Operators (Transact-SQL)
SELECT Examples (Transact-SQL)
Help and Information
Getting SQL Server 2005 Assistance
Change History
| Release | History |
|---|---|
14 April 2006 |
|