追加の作業の後、Artの回答でこのアプローチを使用しないことにしました（それが機能したとしても）。
サブストリングを検証および抽出するためのはるかに強力な方法が必要だったので、CLRルートを介して正規表現を使用しました（正しい方向に向けてくれたPondlifeに感謝します）。
私が取ったアプローチは次のとおりです。
最初に私は次のCLRをコンパイルしました:(ここでC＃の例からVBに変換されました）
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.Text.RegularExpressions
Imports System.Text
Partial Public Class UserDefinedFunctions
Public Shared ReadOnly Options As RegexOptions = RegexOptions.IgnorePatternWhitespace Or RegexOptions.Multiline
<SqlFunction()> _
Public Shared Function RegexMatch(ByVal input As SqlChars, ByVal pattern As SqlString) As SqlBoolean
Dim regex As New Regex(pattern.Value, Options)
Return regex.IsMatch(New String(input.Value))
End Function
<SqlFunction()> _
Public Shared Function RegexReplace(ByVal expression As SqlString, ByVal pattern As SqlString, ByVal replace As SqlString) As SqlString
If expression.IsNull OrElse pattern.IsNull OrElse replace.IsNull Then
Return SqlString.Null
End If
Dim r As New Regex(pattern.ToString())
Return New SqlString(r.Replace(expression.ToString(), replace.ToString()))
End Function
' returns the matching string. Results are separated by 3rd parameter
<SqlFunction()> _
Public Shared Function RegexSelectAll(ByVal input As SqlChars, ByVal pattern As SqlString, ByVal matchDelimiter As SqlString) As SqlString
Dim regex As New Regex(pattern.Value, Options)
Dim results As Match = regex.Match(New String(input.Value))
Dim sb As New StringBuilder()
While results.Success
sb.Append(results.Value)
results = results.NextMatch()
' separate the results with newline|newline
If results.Success Then
sb.Append(matchDelimiter.Value)
End If
End While
Return New SqlString(sb.ToString())
End Function
' returns the matching string
' matchIndex is the zero-based index of the results. 0 for the 1st match, 1, for 2nd match, etc
<SqlFunction()> _
Public Shared Function RegexSelectOne(ByVal input As SqlChars, ByVal pattern As SqlString, ByVal matchIndex As SqlInt32) As SqlString
Dim regex As New Regex(pattern.Value, Options)
Dim results As Match = regex.Match(New String(input.Value))
Dim resultStr As String = ""
Dim index As Integer = 0
While results.Success
If index = matchIndex Then
resultStr = results.Value.ToString()
End If
results = results.NextMatch()
index += 1
End While
Return New SqlString(resultStr)
End Function
End Class
このCLRを次のようにインストールしました。
EXEC sp_configure
'clr enabled' ,
'1'
GO
RECONFIGURE
USE [db_Utility]
GO
CREATE ASSEMBLY SQL_CLR_RegExp FROM 'D:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Binn\SQL_CLR_RegExp.dll' WITH
PERMISSION_SET = SAFE
GO
-- =============================================
-- Returns 1 or 0 if input matches pattern
-- VB function: RegexMatch(ByVal input As SqlChars, ByVal pattern As SqlString) As SqlBoolean
-- =============================================
CREATE FUNCTION [dbo].[RegexMatch]
(
@input [nvarchar](MAX) ,
@pattern [nvarchar](MAX)
)
RETURNS [bit]
WITH EXECUTE AS CALLER
AS EXTERNAL NAME
[SQL_CLR_RegExp].[SQL_CLR_RegExp.UserDefinedFunctions].[RegexMatch]
GO
-- =============================================
-- Returns a comma separated string of found objects
-- VB function: RegexReplace(ByVal expression As SqlString, ByVal pattern As SqlString, ByVal replace As SqlString) As SqlString
-- =============================================
CREATE FUNCTION [dbo].[RegexReplace]
(
@expression [nvarchar](MAX) ,
@pattern [nvarchar](MAX) ,
@replace [nvarchar](MAX)
)
RETURNS [nvarchar](MAX)
WITH EXECUTE AS CALLER
AS EXTERNAL NAME
[SQL_CLR_RegExp].[SQL_CLR_RegExp.UserDefinedFunctions].[RegexReplace]
GO
-- =============================================
-- Returns a comma separated string of found objects
-- VB function: RegexSelectAll(ByVal input As SqlChars, ByVal pattern As SqlString, ByVal matchDelimiter As SqlString) As SqlString
-- =============================================
CREATE FUNCTION [dbo].[RegexSelectAll]
(
@input [nvarchar](MAX) ,
@pattern [nvarchar](MAX) ,
@matchDelimiter [nvarchar](MAX)
)
RETURNS [nvarchar](MAX)
WITH EXECUTE AS CALLER
AS EXTERNAL NAME
[SQL_CLR_RegExp].[SQL_CLR_RegExp.UserDefinedFunctions].[RegexSelectAll]
GO
-- =============================================
-- Returns finding matchIndex of a zero based index
-- RegexSelectOne(ByVal input As SqlChars, ByVal pattern As SqlString, ByVal matchIndex As SqlInt32) As SqlString
-- =============================================
CREATE FUNCTION [dbo].[RegexSelectOne]
(
@input [nvarchar](MAX) ,
@pattern [nvarchar](MAX) ,
@matchIndex [int]
)
RETURNS [nvarchar](MAX)
WITH EXECUTE AS CALLER
AS EXTERNAL NAME
[SQL_CLR_RegExp].[SQL_CLR_RegExp.UserDefinedFunctions].[RegexSelectOne]
GO
次に、使用を簡単にするために次のラッピング関数を作成しました。
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: <Jordon Pilling>
-- Create date: <30/01/2013>
-- Description: <Calls RegexSelectOne with start and end text and cleans the result>
-- =============================================
CREATE FUNCTION [dbo].[RegexSelectOneWithScrub]
(
@Haystack VARCHAR(MAX),
@StartNeedle VARCHAR(MAX),
@EndNeedle VARCHAR(MAX)
)
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE @ReturnStr VARCHAR(MAX)
--#### Extract text from HayStack using Start and End Needles
SET @ReturnStr = dbo.RegexSelectOne(@Haystack, REPLACE(@StartNeedle, ' ','\s') + '((.|\n)+?)' + REPLACE(@EndNeedle, ' ','\s'), 0)
--#### Remove the Needles
SET @ReturnStr = REPLACE(@ReturnStr, @StartNeedle, '')
SET @ReturnStr = REPLACE(@ReturnStr, @EndNeedle, '')
--#### Trim White Space
SET @ReturnStr = LTRIM(RTRIM(@ReturnStr))
--#### Trim Line Breaks and Carriage Returns
SET @ReturnStr = dbo.SuperTrim(@ReturnStr)
RETURN @ReturnStr
END
GO
これにより、次のように使用できるようになりました。
DECLARE @Subject VARCHAR(250) = 'HelpDesk Call Reference F0012345, Call Update, 40111'
DECLARE @Ref VARCHAR(250) = NULL
IF dbo.RegexMatch(@Subject, '^HelpDesk\sCall\sReference\sF[0-9]{7},\s(Call\sResolved|Call\sUpdate|New\scall\slogged),(|\s+)([0-9]+|unknown)$') = 1
SET @Ref = ISNULL(dbo.RegexSelectOneWithScrub(@Subject, 'HelpDesk Call Reference', ','), 'Invalid (#1)')
ELSE
SET @Ref = 'Invalid (#2)'
SELECT @Ref
これは、複数の検索に使用するのがはるかに速く、開始フレーズと終了フレーズなどが異なる大量のテキストを処理する場合にはるかに強力です。
