Look at the following "Products" table:

P_Id ProductName UnitPrice UnitsInStock UnitsOnOrder
1 Jarlsberg 10.45 16 15
2 Mascarpone 32.56 23  
3 Gorgonzola 15.67 9 20


Suppose that the "UnitsOnOrder" column is optional, and may contain NULL values.

Look at the following SELECT statement:
 
SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder)
FROM Products;

In the example above, if any of the "UnitsOnOrder" values are NULL, the result will be NULL.
 



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