How to Efficiently Remove Non-Latin Characters (like Â) from SQL Server VARCHAR Columns?

How to clear non-Latin characters (such as Â) in SQL Server VARCHAR columns

When importing data from third-party data sources (such as CSV files), you often encounter strange characters (such as Â) in SQL Server VARCHAR columns. This is a common problem caused by uncertain encoding methods. However, there are efficient ways to clean and remove these characters, both at the database level and at the code level.

Database-level solution: SQL CLR functions

Since SQL Server does not natively support regular expressions, you can create a SQL CLR function to take advantage of .NET's regular expression capabilities. The specific steps are as follows:

1. Create a C# class library project in Visual Studio.
2. Rename the default class to StackOverflow and paste the following code:

public class StackOverflow
{
    [SqlFunction(DataAccess = DataAccessKind.None, IsDeterministic = true, Name = "RegexReplace")]
    public static SqlString Replace(SqlString sqlInput, SqlString sqlPattern, SqlString sqlReplacement)
    {
        string input = (sqlInput.IsNull) ? string.Empty : sqlInput.Value;
        string pattern = (sqlPattern.IsNull) ? string.Empty : sqlPattern.Value;
        string replacement = (sqlReplacement.IsNull) ? string.Empty : sqlReplacement.Value;
        return new SqlString(Regex.Replace(input, pattern, replacement));
    }
}

3. Build the project and copy the resulting StackOverflow.dll to a known location on your machine.

4. Import the assembly into SQL Server:

    CREATE ASSEMBLY [StackOverflow] FROM 'path_to_StackOverflow.dll';

5. Create SQL CLR function:

    CREATE FUNCTION [dbo].[StackOverflowRegexReplace] (@input NVARCHAR(MAX),
                                                        @pattern NVARCHAR(MAX),
                                                        @replacement NVARCHAR(MAX))
    RETURNS NVARCHAR(4000)
    AS EXTERNAL NAME [StackOverflow].[StackOverflow].[Replace]
    GO

After creating the function, you can use it directly in a T-SQL statement to quickly and efficiently replace characters:

SELECT [dbo].[StackOverflowRegexReplace] ('Hello Kitty Essential Accessory Kit', '[^\u0000-\u007F]', '')

This will return the string "Hello Kitty Essential Accessory Kit" with the  character removed.

C# code-level solution: Regex.Replace

If you prefer a C# solution, you can use the Regex.Replace method to perform the same character replacement:

string input = "Hello Kitty Essential Accessory Kit";
string output = Regex.Replace(input, @"[^\u0000-\u007F]", string.Empty);
Console.WriteLine(output); // "Hello Kitty Essential Accessory Kit"

This method provides a straightforward and reliable way to eliminate non-Latin characters in C# code.

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