NCHAR (Transact-SQL)

บทความ
12/29/2022

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Returns the Unicode character with the specified integer code, as defined by the Unicode standard.

Transact-SQL syntax conventions

Syntax

NCHAR ( integer_expression )

Arguments

integer_expression
When the collation of the database does not contain the Supplementary Character (SC) flag, this is a positive integer from 0 through 65535 (0 through 0xFFFF). If a value outside this range is specified, NULL is returned. For more information about supplementary characters, see Collation and Unicode Support.

When the collation of the database supports the SC flag, this is a positive integer from 0 through 1114111 (0 through 0x10FFFF). If a value outside this range is specified, NULL is returned.

Return Types

nchar(1) when the default database collation does not support supplementary characters.

nvarchar(2) when the default database collation supports supplementary characters.

If the parameter integer_expression lies in the range 0 - 0xFFFF, only one character is returned. For higher values, NCHAR returns the corresponding surrogate pair. Do not construct a surrogate pair by using NCHAR(<High surrogate>) + NCHAR(\<Low Surrogate>). Instead, use a database collation that supports supplementary characters and then specify the Unicode codepoint for the surrogate pair. The following example demonstrates both the old style method of constructing a surrogate pair and the preferred method of specifying the Unicode codepoint.

CREATE DATABASE test COLLATE Finnish_Swedish_100_CS_AS_SC;  
DECLARE @d NVARCHAR(10) = N'𣅿';
-- Old style method.  
SELECT NCHAR(0xD84C) + NCHAR(0xDD7F);   
  
-- Preferred method.   
SELECT NCHAR(143743);   
  
-- Alternative preferred method.  
SELECT NCHAR(UNICODE(@d));

Examples

A. Using NCHAR and UNICODE

The following example uses the UNICODE and NCHAR functions to print the UNICODE value and the NCHAR (Unicode character) of the second character of the København character string, and to print the actual second character, ø.

DECLARE @nstring NCHAR(8);  
SET @nstring = N'København';  
SELECT UNICODE(SUBSTRING(@nstring, 2, 1)),   
   NCHAR(UNICODE(SUBSTRING(@nstring, 2, 1)));  
GO

Here's the result set.

----------- -   
248         ø  
(1 row(s) affected)

B. Using SUBSTRING, UNICODE, CONVERT, and NCHAR

The following example uses the SUBSTRING, UNICODE, CONVERT, and NCHAR functions to print the character number, the Unicode character, and the UNICODE value of each character in the string København.

-- The @position variable holds the position of the character currently  
-- being processed. The @nstring variable is the Unicode character   
-- string to process.  
DECLARE @position INT, @nstring NCHAR(9);  
-- Initialize the current position variable to the first character in   
-- the string.  
SET @position = 1;  
-- Initialize the character string variable to the string to process.  
-- Notice that there is an N before the start of the string. This   
-- indicates that the data following the N is Unicode data.  
SET @nstring = N'København';  
-- Print the character number of the position of the string you are at,   
-- the actual Unicode character you are processing, and the UNICODE   
-- value for this particular character.  
PRINT 'Character #' + ' ' + 'Unicode Character' + ' ' + 'UNICODE Value';  
WHILE @position <= DATALENGTH(@nstring)  
   BEGIN  
   SELECT @position,   
      NCHAR(UNICODE(SUBSTRING(@nstring, @position, 1))),  
      CONVERT(NCHAR(17), SUBSTRING(@nstring, @position, 1)),  
      UNICODE(SUBSTRING(@nstring, @position, 1))  
   SELECT @position = @position + 1  
   END;  
GO

Here's the result set.

Character # Unicode Character UNICODE Value  
  
----------- ---- ----------------- -----------   
1           K    K                 75  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
2           ø    ø                 248  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
3           b    b                 98  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
4           e    e                 101  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
5           n    n                 110  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
6           h    h                 104  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
7           a    a                 97  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
8           v    v                 118  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
9           n    n                 110  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
10          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
11          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
12          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
13          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
14          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
15          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
16          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
17          NULL                   NULL  
  
(1 row(s) affected)  
  
----------- ---- ----------------- -----------   
18          NULL                   NULL  
  
(1 row(s) affected)

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