The Upper() function is used to convert any lower case characters to upper case e.g. a, b, c, d will be A, B, C, D. The second optional parameter require name of culture like fr-FR, en-US, zh-CN and uses that culture information to do the conversion.

SELECT Upper('SQLDatabase.Net') /* returns : SQLDATABASE.NET */ ;

SELECT Upper('SQLDatabase.Net', 'en-GB') /* returns : SQLDATABASE.NET */;

The both statements above will produce the same result of SQLDATABASE.NET