How to Eliminate Unusual Characters (Like Accented Characters) from a SQL Server Varchar Column Using .NET and SQL CLR?

Clear special characters (accented A) in SQL Server varchar columns

Question:

Unexpected characters, such as "accented A", are sneaking into the varchar column of the table. These unwanted visitors are most likely coming from CSV feeds, making it difficult to trace their origin. How can we quickly clean the columns and eliminate these unwanted characters at database level and in C#?

Solution:

.NET regular expression function

In the vast world of .NET, we have found a powerful ally in regular expression functions like Regex.Replace. This powerful tool allows us to unleash the power of pattern matching and manipulation to easily erase unwanted characters:

<code>Regex.Replace(s, @"[^\u0000-\u007F]", string.Empty);</code>

SQL CLR functions

Alas, SQL Server lacks native support for regular expressions, but SQL CLR functions can bridge this gap. Through the integration of .NET and SQL Server, we can use the powerful functions of .NET functions in T-SQL statements.

Step-by-step guide to creating SQL CLR functions:

1. Call Visual Studio and call the class library project.
2. Name the project "StackOverflow" and inject the following code into it:

<code>// .NET正则表达式在SQL CLR函数中

using Microsoft.SqlServer.Server;
using System;
using System.Collections.Generic;
using System.Data.SqlTypes;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

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));
    }
}</code>

3. Show the power of your creation by building projects. Go into the temple of SQL Server Management Studio and guide it to the path to the database. Armed with this knowledge, the following command will create the path to StackOverflow.dll for you:

   <code> CREATE ASSEMBLY [StackOverflow] FROM 'C:\Users\gotqn\Desktop\StackOverflow\StackOverflow\bin\Debug\StackOverflow.dll';</code>

4. Create SQL CLR function:

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

Unleash the magic

Your SQL CLR functions are ready to give you direct access to .NET regular expression functions:

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

// Hello Kitty Essential Accessory Kit</code>

With this newfound power, you can easily clean unwanted characters from SQL Server varchar columns, ensuring the purity of your data.

The above is the detailed content of How to Eliminate Unusual Characters (Like Accented Characters) from a SQL Server Varchar Column Using .NET and SQL CLR?. For more information, please follow other related articles on the PHP Chinese website!