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Exemplo de manipulação de cadeia de caracteres Supplementary-Aware

Este exemplo do SQL Server demonstra o processamento de cadeia de caracteres com reconhecimento de caractere suplementar. Este exemplo mostra a implementação de cinco funções de cadeia de caracteres Transact-SQL que fornecem as mesmas funções de manipulação de cadeia de caracteres que as funções internas, mas com capacidade adicional de reconhecimento de caractere suplementar para lidar com cadeias de caracteres Unicode e suplementares. As cinco funções são lens() lefts(), rights(), subs() e replace_s() que são equivalentes às funções internas LEN(), LEFT(), RIGHT(), SUBSTRING() e REPLACE() às funções de cadeia de caracteres.

Pré-requisitos

Para criar e executar este projeto, o seguinte software deve ser instalado:

  • SQL Server ou SQL Server Express. Você pode obter o SQL Server Express gratuitamente no site de Documentação e Exemplos do SQL Server Express

  • O banco de dados AdventureWorks que está disponível no site do Desenvolvedor do SQL Server

  • SDK do .NET Framework 2.0 ou posterior ou Microsoft Visual Studio 2005 ou posterior. Você pode obter o SDK do .NET Framework gratuitamente.

  • Além disso, as seguintes condições devem ser atendidas:

  • A instância do SQL Server que você está usando deve ter a integração CLR habilitada.

  • Para habilitar a integração do CLR, execute as seguintes etapas:

    Habilitando integração CLR

    • Execute os seguintes comandos de Transact-SQL:

    sp_configure 'clr enabled', 1

    GO

    RECONFIGURE

    GO

    Observação

    Para habilitar o CLR, você deve ter ALTER SETTINGS permissão de nível de servidor, que é mantida implicitamente por membros das funções de servidor fixas e sysadmin de serveradmin membros.

  • O banco de dados AdventureWorks deve ser instalado na instância do SQL Server que você está usando.

  • Se você não for um administrador da instância do SQL Server que está usando, deverá ter um administrador concedendo a você a permissão CreateAssembly para concluir a instalação.

Compilando o exemplo

Crie e execute o exemplo usando as seguintes instruções:

  1. Abra um prompt de comando do Visual Studio ou do .NET Framework.

  2. Se necessário, crie um diretório para o exemplo. Para este exemplo, usaremos C:\MySample.

  3. Como este exemplo requer um assembly assinado, crie uma chave assimétrica digitando o comando:

    sn -k SampleKey.snk

  4. Compile o código de exemplo do prompt de linha de comando executando um dos seguintes, dependendo da sua escolha de idioma.

    • Vbc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /keyfile:Key.snk /target:library SurrogateStringFunction.vb

    • Csc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.XML.dll /keyfile:Key.snk /target:library SurrogateStringFunction.cs

  5. Copie o código de instalação Transact-SQL em um arquivo e salve-o como Install.sql no diretório de exemplo.

  6. Implantar o assembly e o procedimento armazenado executando

    • sqlcmd -E -I -i install.sql -v root = "C:\MySample\"

  7. Copie Transact-SQL script de comando de teste em um arquivo e salve-o como test.sql no diretório de exemplo.

  8. Executar o script de teste com o comando a seguir

    • sqlcmd -E -I -i test.sql

  9. Copie o script de limpeza Transact-SQL em um arquivo e salve-o como cleanup.sql no diretório de exemplo.

  10. Executar o script com o comando a seguir

    • sqlcmd -E -I -i cleanup.sql

Exemplo de código

Veja a seguir as listagens de código para este exemplo.

C#

using System;  
using System.Globalization;  
using System.Text;  
  
/// <summary>  
/// Include several string functions for T-SQL to manipulate surrogate characters.  
/// </summary>  
public sealed class SurrogateStringFunction  
{  
/// <summary>  
///  
/// </summary>  
private SurrogateStringFunction()  
{}  
  
/// <summary>  
/// LenS is equal to T-SQL string function LEN() which returns the number  
/// of characters, rather than the number of bytes, of the given string expression.  
/// </summary>  
/// <param name="value">The input string.</param>  
/// <returns>The number of characters in the string.</returns>  
public static long LenS(String value)  
{  
if (value == null) throw new ArgumentNullException("value");  
  
int[] myIndex;  
// Remove trailing spaces for situations when the Transact-SQL variable or table column  
// uses a fixed length datatype such as nchar(50).  
// If the trailing spaces are not excluded, this function will return 50 which is not  
// correct or expected.  
myIndex = StringInfo.ParseCombiningCharacters(value.TrimEnd());  
return (null != myIndex) ? myIndex.Length : 0;  
}  
  
/// <summary>  
/// SubS only support character expression of T-SQL funciton SUBSTRING()  
/// which returns part of a string.  
/// </summary>  
/// <param name="value">The input string.</param>  
/// <param name="start">The position of the first character that will be returned.</param>  
/// <param name="length">The number of characters to return.</param>  
/// <returns>The string found at the starting position for the specified  
/// number characters.</returns>  
  
public static String SubS(String value, int start, int length)  
{  
if (value == null) throw new ArgumentNullException("value");  
if (length < 0)  
                throw new ArgumentException("Invalid length parameter passed to the substring function.");  
  
// In Transact-SQL, the substring method initializes to 1. So, start should be initialized to at least 1.  
// Length also has to be at least 1 or the Transact-SQL result would be an empty string.  
            if ((start + length) <= 1)  
                return (String.Empty);  
  
// The 2 if statements below guarantee that the result will match the substring function in   
// Transact-SQL which will initialize start to 1 by subtracting from the length.  
            if (start <= 0 && length > 0)  
                length--;  
  
            if ((start <= 0))  
            {  
                length = length + start;  
                start = 1;  
            }  
  
            int[] myIndex;  
myIndex = StringInfo.ParseCombiningCharacters(value);  
int NumOfIndexes = (null != myIndex) ? myIndex.Length : 0;  
  
            start--;  
            if ((0 <= start) && (start < NumOfIndexes))  
{  
int lastIndex = start + length;  
  
// if we are past the last char, then we get the string  
// up to the last char   
if (lastIndex > (NumOfIndexes - 1))  
{  
return value.Substring(myIndex[start]);  
}  
else  
{  
return value.Substring(myIndex[start], myIndex[lastIndex] - myIndex[start]);  
}  
}  
else  
{  
return String.Empty;  
}  
}  
  
//   
//      
/// <summary>  
/// LeftS is equal to T-SQL string function LEFT() which returns the left  
/// part of a character string with the specified number of characters.  
/// </summary>  
/// <param name="value">The input string.</param>  
/// <param name="start">The position of the first character that will be returned.</param>  
/// <param name="length">The number of characters to return.</param>  
/// <returns>The string found at the starting position for n-length.</returns>  
  
public static String LeftS(String value, int length )  
{  
if (length < 0)  
throw new ArgumentException("length must be a positive integer");  
  
return SubS(value, 1, length);  
}  
  
// RightS is equal to T-SQL string function RIGHT() which returns the right  
//    part of a character string with the specified number of characters.  
  
public static String RightS(String value, int length)  
{  
if (length < 0)  
throw new NotSupportedException("length must be a positive integer");  
if (value == null) throw new ArgumentNullException("value");  
  
int[] myIndex;  
  
myIndex = StringInfo.ParseCombiningCharacters(value);  
int numOfIndexes = (null != myIndex) ? myIndex.Length : 0;  
  
if (numOfIndexes <= length)  
return value;  
  
if (length == 0) return String.Empty;  
  
int virtualStartIndex = numOfIndexes - length;  
int physicalStartIndex = myIndex[virtualStartIndex];  
return value.Substring(physicalStartIndex);  
  
}  
  
//  
// ReplaceS is equal to T-SQL string function REPLACE() which replaces all  
// occurrences of the second given string expression in the first string expression  
// with a third expression.  
//  
public static String ReplaceS(String value, String replaceValue, String newValue)  
{  
StringBuilder result = new StringBuilder(value.Length);  
int[] myIndex;  
int i = 0;  
String upperValue = value.ToUpper(CultureInfo.CurrentUICulture);  
String upperReplaceValue = replaceValue.ToUpper(CultureInfo.CurrentUICulture);  
  
myIndex = StringInfo.ParseCombiningCharacters(upperValue);  
while (i < value.Length)  
{  
int possibleMatch = upperValue.IndexOf(upperReplaceValue, i);  
if (possibleMatch < 0)  
{  
result.Append(value.Substring(i));  
break;  
}  
else  
{  
//Ensure we're not matching a partial surrogate  
int surrogateIndex = Array.IndexOf<int>(myIndex, possibleMatch);  
if (surrogateIndex < 0)  
{  
//We've matched in the middle of a surrogate, skip this match  
//as it is not valid.  
int nextStart = possibleMatch + 1;  
result.Append(value.Substring(i, nextStart-i));  
i = nextStart;  
}  
else  
{  
//This is a valid match.  Make the substitution.  
result.Append(value.Substring(i, possibleMatch - i));  
result.Append(newValue);  
i = possibleMatch + replaceValue.Length;  
}  
}  
}  
return result.ToString();  
}  
}

Visual Basic

Imports Microsoft.VisualBasic  
Imports System  
Imports System.Collections  
Imports System.Data  
Imports System.Diagnostics  
Imports System.Globalization  
Imports System.Text  
''' <summary>  
''' Include several string functions for T-SQL to manipulate surrogate characters.  
''' </summary>  
  
Public NotInheritable Class SurrogateStringFunction  
    ''' <summary>  
    ''' Empty default constructor  
    ''' </summary>  
    Private Sub New()  
    End Sub  
  
    ''' <summary>  
    ''' LenS is equal to T-SQL string function LEN() which returns the number  
    ''' of characters, rather than the number of bytes, of the given string expression.  
    ''' </summary>  
    ''' <param name="value">The input string.</param>  
    ''' <returns>The number of characters in the string.</returns>  
    <Microsoft.SqlServer.Server.SqlFunction()> _  
    Public Shared Function LenS(ByVal value As String) As Long  
        If value Is Nothing Then  
            Throw New ArgumentNullException("value")  
        End If  
  
        Dim myIndex() As Integer  
        ' Remove trailing spaces for situations when the Transact-SQL variable or table column  
        ' uses a fixed length datatype such as nchar(50).  
        ' If the trailing spaces are not excluded, this function will return 50 which is not  
        ' correct or expected.  
        myIndex = StringInfo.ParseCombiningCharacters(value.TrimEnd())  
  
        If (myIndex IsNot Nothing) Then  
            Return myIndex.Length  
        Else  
            Return 0  
        End If  
    End Function  
  
    ''' <summary>  
    ''' SubS only support character expression of T-SQL funciton SUBSTRING()  
    ''' which returns part of a string.  
    ''' </summary>  
    ''' <param name="value">The input string.</param>  
    ''' <param name="start">The position of the first character that will be returned.</param>  
    ''' <param name="length">The number of characters to return.</param>  
    ''' <returns>The string found at the starting position for the specified  
    ''' number characters.</returns>  
    <Microsoft.SqlServer.Server.SqlFunction()> _  
    Public Shared Function SubS(ByVal value As String, ByVal start As Integer, ByVal length As Integer) As String  
        If value Is Nothing Then  
            Throw New ArgumentNullException("value")  
        End If  
  
        If length < 0 Then  
            Throw New ArgumentException("Invalid length parameter passed to the substring function.")  
        End If  
  
        ' In Transact-SQL, the substring method initializes to 1. So, start should be initialized to at least 1.  
        ' Length also has to be at least 1 or the Transact-SQL result would be an empty string.  
        If start + length <= 1 Then  
            Return String.Empty  
        End If  
  
        ' The 2 if statements below guarantee that the result will match the substring function in   
        ' Transact-SQL which will initialize start to 1 by subtracting from the length.  
        If start <= 0 AndAlso length > 0 Then  
            length -= 1  
        End If  
  
        If start <= 0 Then  
            length = length + start  
            start = 1  
        End If  
  
        Dim myIndex() As Integer  
        myIndex = StringInfo.ParseCombiningCharacters(value)  
  
        Dim NumOfIndexes As Integer  
        If (myIndex IsNot Nothing) Then  
            NumOfIndexes = myIndex.Length  
        Else  
            NumOfIndexes = 0  
        End If  
  
        start -= 1  
        If 0 <= start AndAlso start < NumOfIndexes Then  
            Dim lastIndex As Integer = start + length  
  
            ' if we are past the last char, then we get the string  
            ' up to the last char   
            If lastIndex > NumOfIndexes - 1 Then  
                Return value.Substring(myIndex(start))  
            Else  
                Return value.Substring(myIndex(start), myIndex(lastIndex) - myIndex(start))  
            End If  
        Else  
            Return String.Empty  
        End If  
    End Function  
  
    ''' <summary>  
    ''' LeftS is equal to T-SQL string function LEFT() which returns the left  
    ''' part of a character string with the specified number of characters.  
    ''' </summary>  
    ''' <param name="value">The input string.</param>  
    ''' <param name="length">The number of characters to return.</param>  
    ''' <returns>The string found at the starting position for n-length.</returns>  
    <Microsoft.SqlServer.Server.SqlFunction()> _  
    Public Shared Function LeftS(ByVal value As String, ByVal length As Integer) As String  
        If length < 0 Then  
            Throw New ArgumentException("Length must be a positive integer")  
        End If  
  
        Return SubS(value, 1, length)  
    End Function  
  
    ' RightS is equal to T-SQL string function RIGHT() which returns the right  
    '    part of a character string with the specified number of characters.  
    <Microsoft.SqlServer.Server.SqlFunction()> _  
    Public Shared Function RightS(ByVal value As String, ByVal length As Integer) As String  
        If value Is Nothing Then  
            Throw New ArgumentNullException("value")  
        End If  
  
        If length < 0 Then  
            Throw New NotSupportedException("Length must be a positive integer")  
        End If  
  
        Dim myIndex() As Integer  
  
        myIndex = StringInfo.ParseCombiningCharacters(value)  
        Dim NumOfIndexes As Integer  
        If (myIndex IsNot Nothing) Then  
            NumOfIndexes = myIndex.Length  
        Else  
            NumOfIndexes = 0  
        End If  
  
        If NumOfIndexes <= length Then  
            Return value  
        End If  
  
        If length = 0 Then  
            Return String.Empty  
        End If  
  
        Dim virtualStartIndex As Integer = NumOfIndexes - length  
        Dim physicalStartIndex As Integer = myIndex(virtualStartIndex)  
  
        Return value.Substring(physicalStartIndex)  
    End Function  
  
    ''' <summary>  
    ''' ReplaceS is equal to T-SQL string function REPLACE() which replaces all  
    ''' occurrences of the second given string expression in the first string expression  
    ''' with a third expression.  
    ''' </summary>  
    ''' <param name="value"></param>  
    ''' <param name="replaceValue"></param>  
    ''' <param name="newValue"></param>  
    ''' <returns></returns>  
    ''' <remarks></remarks>  
    <Microsoft.SqlServer.Server.SqlFunction()> _  
    Public Shared Function ReplaceS(ByVal value As String, ByVal replaceValue As String, ByVal newValue As String) As String  
        Dim result As New StringBuilder(value.Length)  
        Dim myIndex() As Integer  
        Dim i As Integer = 0  
        Dim upperValue As String = value.ToUpper(CultureInfo.CurrentUICulture)  
        Dim upperReplaceValue As String = replaceValue.ToUpper(CultureInfo.CurrentUICulture)  
  
        myIndex = StringInfo.ParseCombiningCharacters(upperValue)  
  
        While i < value.Length  
            Dim possibleMatch As Integer = upperValue.IndexOf(upperReplaceValue, i)  
            If possibleMatch < 0 Then  
                result.Append(value.Substring(i))  
                Exit While  
            Else  
                'Ensure we're not matching a partial surrogate  
                Dim surrogateIndex As Integer = Array.IndexOf(Of Integer)(myIndex, possibleMatch)  
                If surrogateIndex < 0 Then  
                    'We've matched in the middle of a surrogate, skip this match  
                    'as it is not valid.  
                    Dim nextStart As Integer = possibleMatch + 1  
                    result.Append(value.Substring(i, nextStart - i))  
                    i = nextStart  
                Else  
                    'This is a valid match.  Make the substitution.  
                    result.Append(value.Substring(i, possibleMatch - i))  
                    result.Append(newValue)  
                    i = possibleMatch + replaceValue.Length  
                End If  
            End If  
        End While  
  
        Return result.ToString()  
    End Function  
End Class

Esse é o Transact-SQL script de instalação (Install.sql), que implanta o assembly e cria as funções com reconhecimento suplementar no banco de dados.

Use [AdventureWorks]  
Go  
  
IF OBJECT_ID('[dbo].[len_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[len_s];  
  
IF OBJECT_ID('[dbo].[sub_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[sub_s];  
  
IF OBJECT_ID('[dbo].[left_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[left_s];  
  
IF OBJECT_ID('[dbo].[right_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[right_s];  
  
IF OBJECT_ID('[dbo].[replace_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[replace_s];  
GO  
  
IF EXISTS (SELECT [name] FROM sys.assemblies  
             WHERE [name] = 'SurrogateStringFunction')  
  DROP ASSEMBLY SurrogateStringFunction;  
GO  
  
USE master  
GO  
  
IF EXISTS (SELECT * FROM sys.server_principals WHERE [name] = 'ExternalSample_Login')  
DROP LOGIN ExternalSample_Login;  
GO  
  
IF EXISTS (SELECT * FROM sys.asymmetric_keys WHERE [name] = 'ExternalSample_Key')  
DROP ASYMMETRIC KEY ExternalSample_Key;  
GO  
  
--Before we register the assembly to SQL Server, we must arrange for the appropriate permissions.  
--Assemblies with unsafe or external_access permissions can only be registered and operate correctly  
--if either the database trustworthy bit is set or if the assembly is signed with a key,  
--that key is registered with SQL Server, a server principal is created from that key,  
--and that principal is granted the external access or unsafe assembly permission.  We choose  
--the latter approach as it is more granular, and therefore safer.  You should never  
--register an assembly with SQL Server (especially with external_access or unsafe permissions) without  
--thoroughly reviewing the source code of the assembly to make sure that its actions   
--do not pose an operational or security risk for your site.  
  
DECLARE @SamplesPath nvarchar(1024);  
  
-- You may need to modify the value of the this variable if you have installed the sample someplace other than the default location.  
set @SamplesPath = N'C:\MySample\'  
  
EXEC('CREATE ASYMMETRIC KEY ExternalSample_Key FROM EXECUTABLE FILE = ''' + @SamplesPath   
    + 'SurrogateStringFunction.dll'';');  
CREATE LOGIN ExternalSample_Login FROM ASYMMETRIC KEY ExternalSample_Key  
GRANT EXTERNAL ACCESS ASSEMBLY TO ExternalSample_Login;  
GO  
  
USE AdventureWorks;  
GO  
  
--  
-- Create assembly to register class methods for create functions  
--   
DECLARE @SamplesPath nvarchar(1024);  
-- You may need to modify the value of the this variable if you have installed the sample someplace other than the default location.  
  
set @SamplesPath = N'C:\MySample\'  
  
CREATE ASSEMBLY [SurrogateStringFunction]  
FROM @SamplesPath + 'SurrogateStringFunction.dll'  
WITH PERMISSION_SET = EXTERNAL_ACCESS;  
GO  
  
CREATE FUNCTION [dbo].[len_s] (@str nvarchar(4000))  
RETURNS bigint  
AS EXTERNAL NAME [SurrogateStringFunction].[SurrogateStringFunction].[LenS];  
GO  
  
CREATE FUNCTION [dbo].[sub_s](@str nvarchar(4000), @pos int, @cont int)  
RETURNS nvarchar(4000)  
AS EXTERNAL NAME [SurrogateStringFunction].[SurrogateStringFunction].[SubS];  
GO  
  
CREATE FUNCTION [dbo].[left_s](@str nvarchar(4000), @cont int)  
RETURNS nvarchar(4000)  
AS EXTERNAL NAME [SurrogateStringFunction].[SurrogateStringFunction].[LeftS];  
GO  
  
CREATE FUNCTION [dbo].[right_s](@str nvarchar(4000), @cont int)  
RETURNS nvarchar(4000)  
AS EXTERNAL NAME [SurrogateStringFunction].[SurrogateStringFunction].[RightS];  
GO  
  
CREATE FUNCTION [dbo].[replace_s](@str nvarchar(4000), @str1 nvarchar(4000), @str2 nvarchar(4000))  
RETURNS nvarchar(4000)  
AS EXTERNAL NAME [SurrogateStringFunction].[SurrogateStringFunction].[ReplaceS];  
GO

Isto é test.sql, que testa o exemplo executando as funções.

Use [AdventureWorks]  
Go  
  
-- left_s  VS  Left  
print ('***** left_s VS Left *****');  
select [dbo].[left_s](N'𠱷𠱸123',2);  
print(N'Should Return 𠱷𠱸');  
go  
select Left(N'𠱷𠱸123',2);  
print(N'Will Return 𠱷');  
go  
  
-- right_s VS Right  
print ('***** right_s VS Right *****')  
select [dbo].[right_s](N'𠱷𠱸123',5);  
print(N'Should Return 𠱷𠱸123');  
go  
select Right(N'𠱷𠱸123',5);  
print(N'Will Return 𠱸123');  
go  
  
-- len_s  VS Len  
print('***** len_s VS Len *****');  
select [dbo].[len_s](N'𠆾𠇀𠇃12');  
print(N'Should Return 5');  
go  
select Len(N'𠆾𠇀𠇃12');  
print(N'Will Return 8');  
go  
  
-- sub_s VS Substring  
print('***** sub_s VS Subscription *****');  
select [dbo].[sub_s] (N'𢙢𢙣𢙤𢙥𢙦𢙧𢙨𢙩𢙪𢙫𢙬𢙭𢙮𢙯𢙰𢙱𢙲𢙳',3,5);  
print(N'Should Return 𢙤𢙥𢙦𢙧𢙨');  
go  
select substring(N'𢙢𢙣𢙤𢙥𢙦𢙧𢙨𢙩𢙪𢙫𢙬𢙭𢙮𢙯𢙰𢙱𢙲𢙳',3,5);  
print(N'Will Return 𢙣𢙤');  
go  
  
-- replace_s VS Replace  
print('***** replace_s VS Replace *****');  
select [dbo].[replace_s](N'𡥕𡥖𡥗𡥙𡥚𡥛𡥕𡥖𡥗𡥙𡥚𡥛',N'𡥗𡥙𡥚',N'𡦼');  
print(N'Should Return 𡥖𡦼𡥛𡥕𡥖𡦼𡥛');  
go  
select replace(N'𡥕𡥖𡥗𡥙𡥚𡥛𡥕𡥖𡥗𡥙𡥚𡥛',N'𡥗𡥙𡥚',N'𡦼');  
print(N'Will Return 𡦼');  
go

O Transact-SQL a seguir remove o assembly e as funções do banco de dados.

-- Drop assemblies and functions if they exist.  
USE [AdventureWorks]  
GO  
  
IF OBJECT_ID('[dbo].[len_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[len_s];  
  
IF OBJECT_ID('[dbo].[sub_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[sub_s];  
  
IF OBJECT_ID('[dbo].[left_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[left_s];  
  
IF OBJECT_ID('[dbo].[right_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[right_s];  
  
IF OBJECT_ID('[dbo].[replace_s]') IS NOT NULL  
  DROP FUNCTION [dbo].[replace_s];  
GO  
  
IF EXISTS (SELECT [name] FROM sys.assemblies  
             WHERE [name] = 'SurrogateStringFunction')  
  DROP ASSEMBLY SurrogateStringFunction;  
GO  
  
USE master  
GO  
  
IF EXISTS (SELECT * FROM sys.server_principals WHERE [name] = 'ExternalSample_Login')  
DROP LOGIN ExternalSample_Login;  
GO  
  
IF EXISTS (SELECT * FROM sys.asymmetric_keys WHERE [name] = 'ExternalSample_Key')  
DROP ASYMMETRIC KEY ExternalSample_Key;  
GO  
  
USE [AdventureWorks]  
GO

Consulte Também

Cenários de uso e exemplos para a integração de CLR (Common Language Runtime)

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