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Use a subquery with NOT EXISTS to find unrelated records

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This article is from the book "Access 2007 Pure SQL

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Use a subquery with NOT EXISTS to find unrelated records

Find customers without any orders

Discussion:

This time, we will use NOT EXISTS to find customers who have not submitted any orders at all.  Thus, we are trying to find customers without any related orders in the orders table.  This is not a problem when it comes to database integrity.  It is just a business fact.  We might want to initiate a promotional campaign for these customers, for example. 

Code:

SELECT *

FROM Customers C

WHERE NOT EXISTS (SELECT CustomerID FROM Orders O WHERE C.CustomerID = O.CustomerID)

 

Result: