CSV formats are not limited to a particular character set. They work just as well with Unicode character sets (such as UTF-8 or UTF-16) as with ASCII (although particular programs that support CSV may have their own limitations). CSV files normally will even survive naive translation from one character set to another (unlike nearly all proprietary data formats). CSV does not, however, provide any way to indicate what character set is in use, so that must be communicated separately, or determined at the receiving end (if possible).
Databases that include multiple relations cannot be exported as a single CSV file.
Microsoft Excel will open .csv files, but depending on the system's regional settings, it may expect a semicolon as a separator instead of a comma, since in some languages the comma is used as the decimal separator. It also applies some magic, such as reformatting what looks like numbers, eliminating leading + or 0, which breaks phone numbers, or a leading = makes the cell a formula, where function names must be in the opener's local language. Also, many regional versions of Excel will not be able to deal with Unicode in CSV. One simple solution when encountering such difficulties is to change the filename extension from .csv to .txt; then opening the file from an already running Excel instance with the "Open" command, where the user can manually specify the delimiters, encoding, format of columns, etc.