SQL EXCEPT and INTERSECT

-- AdventureWorks DB

SELECT ProductID   
FROM Production.Product  
INTERSECT  
SELECT ProductID   
FROM Production.WorkOrder ;

==== Gives ONLY matching ProductIDs..

SELECT ProductID   
FROM Production.Product  
EXCEPT  
SELECT ProductID   
FROM Production.WorkOrder ;  
--Result: 266 Rows (products without work orders)

==== Gives ProductIDs from Left Set which are NOT in the right Set.