Why is T-SQL ISNULL() truncating the string and COALESCE is not?

Question

Given the following:

SELECT ISNULL(\'XY\' + NULL, \'ABCDEFGHIJ\') -- Outputs ABC (Why?)
SELECT COALESCE(\'XY\' + NULL, \'ABCDEFGHIJ\') -- Outputs ABCDEFGHIJ
         


        

Answer 1

You can check all the difference here, its very clear

MSDN : http://msdn.microsoft.com/en-us/library/ms190349.aspx

MSDN Blog : http://blogs.msdn.com/b/sqltips/archive/2008/06/26/differences-between-isnull-and-coalesce.aspx