Microsoft SQL Server NULLs COALESCE ()
Example
COALESCE () Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL.
DECLARE @MyInt int -- variable is null until it is set with value.
DECLARE @MyInt2 int -- variable is null until it is set with value.
DECLARE @MyInt3 int -- variable is null until it is set with value.
SET @MyInt3 = 3
SELECT COALESCE (@MyInt, @MyInt2 ,@MyInt3 ,5) -- Returns 3 : value of @MyInt3.
Although ISNULL() operates similarly to COALESCE(), the ISNULL() function only accepts two parameters - one to check, and one to use if the first parameter is NULL.
See also ISNULL, below
