LEN and DATALENGTH in SQL Server

Difference between LEN and DATALENGTH in SQL Server

Len will trim the end of the string and count the length where as  DATALENGTH just count the lenght,its doesn't trim :)

Below sample query and example

DECLARE @str VARCHAR(50)
SET @str='Arun Aravind '
SELECT LEN(@str) AS LenCount
SELECT DATALENGTH(@str) AS DataLengthCount

If u had any trouble just ask, Happy to help u :) 
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Have a nice day... 'N happy Coding :)