You use the NVARCHAR2 datatype to store variable-length Unicode character data. How the data is represented internally depends on the national character set specified when the database was created, which might use a variable-width encoding (UTF8) or a fixed-width encoding (AL16UTF16). Because this type can always accommodate multibyte characters, you can use it to hold any Unicode character data.
The NVARCHAR2 datatype takes a required parameter that specifies a maximum size in characters. The syntax follows:
NVARCHAR2(maximum_size)
Because the physical limit is 32767 bytes, the maximum value you can specify for the length is 32767/2 in the AL16UTF16 encoding, and 32767/3 in the UTF8 encoding.
You cannot use a symbolic constant or variable to specify the maximum size; you must use an integer literal.
The maximum size always represents the number of characters, unlike VARCHAR2 which can be specified in either characters or bytes.
my_string NVARCHAR2(200); -- maximum size is 200 characters
The maximum width of a NVARCHAR2 database column is 4000 bytes. Therefore, you cannot insert NVARCHAR2 values longer than 4000 bytes into a NVARCHAR2 column
