nchar and nvarchar (Transact-SQL)
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. The storage size is two times n bytes. The ISO synonyms for nchar are national char and national character.
nvarchar [ ( n | max ) ]
Variable-length Unicode character data. ncan be a value from 1 through 4,000. max indicates that the maximum storage size is 2^31-1 bytes. The storage size, in bytes, is two times the number of characters entered + 2 bytes. The data entered can be 0 characters in length. The ISO synonyms for nvarchar are national char varying and national character varying.
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 sizes of the column data entries are probably going to be similar.
Use nvarchar when the sizes of the column data entries are probably going to vary considerably.
sysname is a system-supplied user-defined data type that is functionally equivalent to nvarchar(128), except that it is not nullable. sysname is used to reference database object names.
Objects that use nchar or nvarchar are assigned the default collation of the database unless a specific collation is assigned using the COLLATE clause.
SET ANSI_PADDING is always ON for nchar and nvarchar. SET ANSI_PADDING OFF does not apply to the nchar or nvarchar data types.