How can I change the character set while importing as I have a customer schema in Japanese character set? I see the following warning.

import done in WE8MSWIN1252 character set and AL16UTF16 NCHAR character set
export client uses JA16SJISTILDE character set (possible charset conversion)

Alternatively, I created a new database with JA16SJISTILDE character set but still I see the same warning. The problem is that probably because of no conversion of character set, some unique indexes do not get created gvivng the message "cannot CREATE UNIQUE INDEX; duplicate keys found". When I check the table rows for indexed columns, it shows some rows that look same in present character set. I think if I am able to eliminate the character set problem, I will be able to create unique indexes.