UNISTR takes as its argument a text literal or an expression that resolves to character data and returns it in the national character set. The national character set of the database can be either AL16UTF16 or UTF8. UNISTR provides support for Unicode string literals by letting you specify the Unicode encoding value of characters in the string. This is useful, for example, for inserting data into NCHAR columns.

The Unicode encoding value has the form '\xxxx' where 'xxxx' is the hexadecimal value of a character in UCS-2 encoding format. 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 the backslash in the string itself, precede it with another backslash (\\).

For portability and data preservation, Oracle recommends that in the UNISTR string argument you specify only ASCII characters and the Unicode encoding values.

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The following example passes both ASCII characters and Unicode encoding values to the UNISTR function, which returns the string in the national character set:

SELECT UNISTR('abc\00e5\00f1\00f6') FROM DUAL;