Образец операций над строками с учетом дополнений

Статья
05/07/2013

В данном образце для SQL Server демонстрируется обработка строк с учетом дополнительных символов. В данном образце показана реализация пяти строковых функций Transact-SQL с такими же возможностями работы со строками, как и во встроенных функциях, но с расширенной поддержкой дополнительных символов при обработке как строк в Юникоде, так и строк дополнительных символов. Вот эти пять функций: lens(), lefts(), rights(), subs() и replace_s(), которые эквивалентны встроенным строковым функциям LEN(), LEFT(), RIGHT(), SUBSTRING() и REPLACE().

Предварительные требования

Для создания и запуска этого проекта должно быть установлено следующее программное обеспечение:

SQL Server или SQL Server Express. SQL Server Express можно получить бесплатно с веб-сайтадокументации и образцов SQL Server Express (возможно, на английском языке)
База данных AdventureWorks, которая доступна на веб-сайте разработки SQL Server (возможно, на английском языке)
Пакет SDK 2.0 для платформы .NET Framework или более поздняя версия либо среда Microsoft Visual Studio 2005 или более поздняя версия. Пакет SDK для платформы .NET Framework можно получить бесплатно.
Кроме того, должны выполняться следующие условия.
Для используемого экземпляра SQL Server должна быть включена интеграция со средой CLR.

Чтобы включить интеграцию со средой CLR, выполните следующие действия.

Включение интеграции со средой CLR

Выполните следующие команды Transact-SQL:

sp_configure 'clr enabled', 1

RECONFIGURE

Примечание
Чтобы включить CLR, необходимо иметь разрешение ALTER SETTINGS на уровне сервера, которое неявно назначается членам предопределенных ролей сервера sysadmin и serveradmin.

На используемом экземпляре SQL Server должна быть установлена база данных AdventureWorks.
Если вы не являетесь администратором используемого экземпляра SQL Server, то для завершения установки необходимо, чтобы администратор предоставил разрешение CreateAssembly .

Построение образца

Создайте и запустите образец в соответствии со следующими инструкциями.

Откройте командную строку Visual Studio или .NET Framework.
Если необходимо, создайте каталог для своего образца. В данном примере будет использоваться каталог C:\MySample.
Поскольку этому примеру требуется подписанная сборка, создайте асимметричный ключ, выполнив следующую команду:

sn -k SampleKey.snk
Скомпилируйте образец кода из командной строки, выполнив одну из следующих команд, в зависимости от выбранного языка.
- 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
Скопируйте код установки Transact-SQL в файл и сохраните его в файле Install.sql в том же каталоге.
Разверните сборку и хранимую процедуру, выполнив
- sqlcmd -E -I -i install.sql -v root = "C:\MySample\"
Скопируйте скрипт проверки Transact-SQL в файл и сохраните его в файле test.sql в том же каталоге.
Выполните скрипт проверки следующей командой
- sqlcmd -E -I -i test.sql
Скопируйте скрипт очистки Transact-SQL в файл и сохраните его в файле cleanup.sql в том же каталоге.
Выполните скрипт следующей командой
- sqlcmd -E -I -i cleanup.sql

Образец кода

Ниже приведены листинги кода для данного образца.

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 guarentee 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 guarentee 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

Это скрипт установки Transact-SQL (Install.sql), который выполняет развертывание сборки и создает в базе данных функции, учитывающие дополнения.

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

Это файл test.sql, который проверяет образец, выполняя его функции.

Use [AdventureWorks]
Go

-- left_s  VS  Left
print ('***** left_s VS Left *****');
select [dbo].[left_s](N'౷౸123',2);
print(N'Should Return ౷౸');
go
select Left(N'౷౸123',2);
print(N'Will Return ౷');
go

-- right_s VS Right
print ('***** right_s VS Right *****')
select [dbo].[right_s](N'౷౸123',5);
print(N'Should Return ౷౸123');
go
select Right(N'౷౸123',5);
print(N'Will Return ౸123');
go

-- len_s  VS Len
print('***** len_s VS Len *****');
select [dbo].[len_s](N'ƾǀǃ12');
print(N'Should Return 5');
go
select Len(N'ƾǀǃ12');
print(N'Will Return 8');
go

-- sub_s VS Substring
print('***** sub_s VS Subscription *****');
select [dbo].[sub_s] (N'♢♣♤♥♦♧♨♩♪♫♬♭♮♯♰♱♲♳',3,5);
print(N'Should Return ♤♥♦♧♨');
go
select substring(N'♢♣♤♥♦♧♨♩♪♫♬♭♮♯♰♱♲♳',3,5);
print(N'Will Return ♣♤');
go

-- replace_s VS Replace
print('***** replace_s VS Replace *****');
select [dbo].[replace_s](N'ᥕᥖᥗᥙᥚᥛᥕᥖᥗᥙᥚᥛ',N'ᥗᥙᥚ',N'ᦼ');
print(N'Should Return ᥖᦼᥛᥕᥖᦼᥛ');
go
select replace(N'ᥕᥖᥗᥙᥚᥛᥕᥖᥗᥙᥚᥛ',N'ᥗᥙᥚ',N'ᦼ');
print(N'Will Return ᦼ');
go

В следующем образце Transact-SQL сборка и функции удаляются из базы данных.

-- 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

См. также

Основные понятия

Сценарии использования и примеры интеграции со средой CLR

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