Sqoop special characters replace

I Have a table in mysql database with column names such as id, name, d.no, loc, sal, d.name.

When I do sqoop import and create table in hive as csv. It throws an error near the columns d.no. But when i do the same as parquet. It creates the table and replaces the . with underscore. why does it do with parquet and not with csv

Can anyone explain

Thank you
Sanjeev