Functions

NULLIF(Quantity,0) 

NULLIF() is a nifty little SQL function that helps you compare two expressions—and if they're equal, it returns NULL. If they're not equal, it returns the first expression.

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ISNULL()

SELECT [FirstName], ISNULL(MiddleName,'--'), [Lastname]  //  return '--' if middlename is null

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COALESCE()

SELECT COALESCE(NULL, NULL, NULL, 'W3Schools.com', NULL, 'Example.com');   // return first non-null value

output:    'W3Schools.com'

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