CROSS JOIN

While the CROSS JOIN is not used much, and, depending on the size of your data it can be dangerous, there are some uses for it. For example, you may want to write a query that will summarize all the sales for the companies and people in your system. You can do this using what is called an aggregate operation or a GROUP BY:

SELECT c.CompanyName,
p.LastName,
SUM(ft.TransactionAmount) AS 'TransactionTotals'
FROM Management.Company AS c
JOIN Finance.FinancialTransaction AS ft
ON c.CompanyID = ft.CompanyID
JOIN Personnel.Person AS p
ON p.PersonID = ft.PersonID
GROUP BY c.CompanyName, p.LastName;

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Overview of SQL Joins in SQL Server

This will add all the values up in the SUM operation for each company and each person that has values so that your data will look like this:


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