Sql server® 2012 t-sql fundamentals

The 

EXCEPT

 distinct Set Operator

The EXCEPT set operator logically first eliminates duplicate rows from the two input multisets—turn-

ing them to sets—and then returns only rows that appear in the first set but not the second. In other 

words, a row is returned provided that it appears at least once in the first input multiset and zero 

times in the second. Note that unlike the other two operators, EXCEPT is asymmetric; that is, with 

the other set operators, it doesn’t matter which input query appears first and which second—with 

EXCEPT, it does.

For example, the following code returns distinct locations that are employee locations but not 

customer locations.

SELECT country, region, city FROM HR.Employees 

EXCEPT 

SELECT country, region, city FROM Sales.Customers;

This query returns the following two locations.

country         region          city 

--------------- --------------- --------------- 

USA             WA              Redmond 

USA             WA              Tacoma

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