UNISTR converts a text string to the national character set.
UNISTR ( string )
string can be any text expression. For portability, Oracle recommends using only ASCII characters and Unicode encoding values as text literals. A Unicode encoding value has the form \xxxx where xxxx is the hexadecimal value of a character. Supplementary characters are encoded as two code units, the first from the high-surrogates range (U+D800 to U+DBFF), and the second from the low-surrogates range (U+DC00 to U+DFFF). To include a literal backslash in the string, precede it with another backslash (\\).
UNISTR('abc\00e5\00f1\00f6') returns the value