I have 150 odd csv files but there file name may vary. so i want to know whether in external table concept can we use *.csv where we provide file name list.
LOCATION (*.csv)
According to this article, you can do it from 12c Release 1 (not tested):
A number of minor usability improvements have been made to the ORACLE_LOADER access driver to make external table creation simpler. The LOCATION clause now accepts wildcards. An "*" matches multiple characters, while a "?" matches a single character.
LOCATION ('emp_ext*.dmp') LOCATION ('emp_ext?.dmp')