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 string data. n defines the string length and must be a value from 1 through 4,000. The storage size is two times n bytes. When the collation code page uses double-byte characters, the storage size is still n bytes. Depending on the string, the storage size of n bytes can be less than the value specified for n. The ISO synonyms for nchar are national char and national character.
nvarchar [ ( n | max ) ]
Variable-length Unicode string data. n defines the string length and can be a value from 1 through 4,000. max indicates that the maximum storage size is 2^30-1 characters. The maximum storage size in bytes is 2 GB. The actual storage size, in bytes, is two times the number of characters entered + 2 bytes. 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.
Prefix Unicode character string constants with the letter N. Without the N prefix, the string is converted to the default code page of the database. This default code page may not recognize certain characters.
When prefixing a string constant with the letter N, the implicit conversion will result in a Unicode string if the constant to convert does not exceed the max length for a Unicode string data type (4,000). Otherwise, the implicit conversion will result in a Unicode large-value (max).
Each non-null varchar(max) or nvarchar(max) column requires 24 bytes of additional fixed allocation, which counts against the 8,060-byte row limit during a sort operation. These additional bytes can create an implicit limit to the number of non-null varchar(max) or nvarchar(max) columns in a table. No special error is provided when the table is created (beyond the usual warning that the maximum row size exceeds the allowed maximum of 8060 bytes) or at the time of data insertion. This large row size can cause errors (such as error 512) that users may not anticipate during some normal operations. Two examples of operations are a clustered index key update, or sorts of the full column set.
Converting Character Data
For information about converting character data, see char and varchar (Transact-SQL).
CREATE TABLE dbo.MyTable ( MyNCharColumn nchar(15) ,MyNVarCharColumn nvarchar(20) ); GO INSERT INTO dbo.MyTable VALUES (N'Test data', N'More test data'); GO SELECT MyNCharColumn, MyNVarCharColumn FROM dbo.MyTable;
Here is the result set.
MyNCharColumn MyNVarCharColumn --------------- -------------------- Test data More test data (1 row(s) affected)
ALTER TABLE (Transact-SQL)
CAST and CONVERT (Transact-SQL)
CREATE TABLE (Transact-SQL)
Data Types (Transact-SQL)
DECLARE @local_variable (Transact-SQL)
SET ANSI_PADDING (Transact-SQL)
SET @local_variable (Transact-SQL)
Collation and Unicode Support