Oracle Tip: The decimal marker to a dot, and the thousands marker to a comma in to_number().

November 17, 2009 by Reboot · Leave a Comment 

to_number(t.yournumbercolumn,'9G999G999D99','NLS_NUMERIC_CHARACTERS='',.''')

See also:

Oracle NLS_NUMERIC_CHARACTERS
http://download.oracle.com/docs/cd/B28359_01/olap.111/b28126/dml_options072.htm