Normalize unicode string in SQL Server?

Question

Is there a function in SQL Server to normalize a unicode string? e.g.

UPDATE Orders SET Notes = NormalizeString(Notes, 'FormC')

Unicode Normalization Forms:

• C​omposition (C): A + ¨ becomes Ä
• D​ecomposition (D): Ä becomes A + ¨
• Compatible Composition (KC): A + ¨ + fi + n becomes Ä + f + i + n
• Compatible Decomposition (KD): Ä + fi + n becomes A + ¨ + f + i + n

i cannot find any built-in function, so i assume there is none.

---

Ideally, if there can be only one, then i happen to need Form C today:

Unicode normalization form C, canonical composition. Transforms each decomposed grouping, consisting of a base character plus combining characters, to the canonical precomposed equivalent. For example, A + ¨ becomes Ä.

See also

• Unicode Normalization in Windows
• How do I remove diacritics (accents) from a string in .NET?
• NormalizeString function
• Sorting it all out: What normalization form does SQL Server use

Answer 1

Sorry, no, there is no such function in any version of SQL Server to date (2012 test builds). Comparisons can be correctly composition-insensitive, but there isn't a function to convert character composition usage to one normal form.

It has been suggested for a future version of the ANSI standard under the syntax NORMALIZE(string, NFC) but it's going to be a long time before this makes it to the real world. For now if you want to do normalisation you'll have to do it in a proper programming language with better string-handling capabilities, either by pulling the string out of the database or by writing a CLR stored procedure to do it.

Answer 2

I was some problem,

I write a new CRL function in C#, and use like a SQL function.

My C# code (nomalize to NFC or NFD). Also, handle NULL string correctly.:

using Microsoft.SqlServer.Server;
using System.Data.SqlTypes;
using System.Text;

    public static class CLRUnicodeNormalize
    {
        [SqlFunction]
        public static SqlString UnicodeNormalizeC(SqlString inStr)
        {
            if (inStr.IsNull) return SqlString.Null;
            return inStr.ToString().Normalize(NormalizationForm.FormC);
        }
        public static SqlString UnicodeNormalizeD(SqlString inStr)
        {
            if (inStr.IsNull) return SqlString.Null;
            return inStr.ToString().Normalize(NormalizationForm.FormD);
        }
    }

Use example in SQL query (form any normalization to C):

UPDATE o SET o.ObjectName=dbo.UnicodeNormalizeC(o.ObjectName)

---

Installing the normalization function before use (you don't need C# in this case... The binary conatains the use-ready .Net code, see source above):

/* 
GO
DROP FUNCTION [dbo].UnicodeNormalize
GO
DROP ASSEMBLY [CLRUnicodeNormalize]
GO
*/


CREATE ASSEMBLY [CLRUnicodeNormalize]
FROM 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WITH PERMISSION_SET = UNSAFE
GO

CREATE FUNCTION [dbo].UnicodeNormalizeC(@inStr nvarchar(max)) RETURNS nvarchar(max) 
AS EXTERNAL NAME [CLRUnicodeNormalize].[CLRUnicodeNormalize].[UnicodeNormalizeC]
GO
CREATE FUNCTION [dbo].UnicodeNormalizeD(@inStr nvarchar(max)) RETURNS nvarchar(max) 
AS EXTERNAL NAME [CLRUnicodeNormalize].[CLRUnicodeNormalize].[UnicodeNormalizeD]
GO

Compiled with .Net version: 4.6

I don't take any resposinbility the use of the binary code above!

Test example:

DECLARE @str_nfd nvarchar(10) = dbo.UnicodeNormalizeD('á');
SELECT LEN(@str_nfd);   -- NFD normalization, return: 2
SELECT LEN(dbo.UnicodeNormalizeC(@str_nfd)); -- back to NFC, return: 1

Answer 3

try this CLR function

using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction]
    public static SqlString fnRemoveDiacritics(string text)
    {
        string stringFormD = text.Normalize(System.Text.NormalizationForm.FormD);
        System.Text.StringBuilder retVal = new System.Text.StringBuilder();
        for (int index = 0; index < stringFormD.Length; index++)
        {
            if (System.Globalization.CharUnicodeInfo.GetUnicodeCategory(stringFormD[index]) != System.Globalization.UnicodeCategory.NonSpacingMark)
                retVal.Append(stringFormD[index]);
        }
        return retVal.ToString().Normalize(System.Text.NormalizationForm.FormC);
    }
}

and in SQL

SELECT dbo.fnRemoveDiacritics('Äěščřžýáíé')
-- Returns: Aescrzyaie

thanks to http://www.dotnetportal.cz/blogy/4/Tomas-Jecha/663/NET-Tip-6-Ciste-odstraneni-diakritiky