nchar and nvarchar
Character data types that are either fixed-length (nchar) or variable-length (nvarchar) Unicode data and use the UNICODE UCS-2 character set.
nchar(n)
Fixed-length Unicode character data of n characters. n must be a value from 1 through 4,000. Storage size is two times n bytes. The SQL-92 synonyms for nchar are national char and national character.
nvarchar(n)
Variable-length Unicode character data of n characters. n must be a value from 1 through 4,000. Storage size, in bytes, is two times the number of characters entered. The data entered can be 0 characters in length. The SQL-92 synonyms for nvarchar are national char varying and national character varying.
Remarks
When n is not specified in a data definition or variable declaration statement, the default length is 1. When n is not specified with the CAST function, the default length is 30.
Use nchar when the data entries in a column are expected to be consistently close to the same size.
Use nvarchar when the data entries in a column are expected to vary considerably in size.
Objects using nchar or nvarchar are assigned the default collation of the database, unless a specific collation is assigned using the COLLATE clause.
SET ANSI_PADDING OFF does not apply to nchar or nvarchar. SET ANSI_PADDING is always ON for nchar and nvarchar.