SELECT *
FROM #testenvironment
WHERE PARSENAME(CAST(yourdata AS NVARCHAR(MAX)),3) IS NULL

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE PARSENAME( CAST(yourData AS NVARCHAR(MAX)),3) IS NULL
AND PARSENAME(CAST(yourData AS NVARCHAR(MAX)), 2) IS NOT NULL

Duration for CHARINDEX = 00:00:18:363
Duration for LEN = 00:00:09:347
Duration for PARSENAME = 00:00:06:870
Duration for COLLATE = 00:00:06:667

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE PARSENAME( CAST(yourData AS NVARCHAR(MAX)),3) IS NULL
AND PARSENAME(CAST(yourData AS NVARCHAR(MAX)), 2) IS NOT NULL

Duration for CHARINDEX = 00:00:18:363
Duration for LEN = 00:00:09:347
Duration for PARSENAME = 00:00:06:870
Duration for COLLATE = 00:00:06:667

SET NOCOUNT ON;
IF object_id('tempdb..#testEnvironment') IS NOT NULL
BEGIN
    DROP TABLE #testEnvironment;
END;
  
--1,000,000 Random rows of data
SELECT IDENTITY(INT,1,1) AS ID, CAST(LEFT(yourData, LEN(yourData) - 1) AS NTEXT) AS yourData
INTO #testEnvironment
FROM (SELECT TOP 1000000 
      REPLICATE(
      REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
      REPLACE(NEWID(),'-','')
      ,'0',''),'9',''),'8',''),'7',''),'6',''),'5',''),'4',''),'3',''),'2',''),'1','') + '.',
      (ABS(CHECKSUM(NEWID())) % 2) + 2)
      FROM master.dbo.syscolumns sc1, master.dbo.syscolumns sc2, master.dbo.syscolumns sc3
      )a(yourData);

DECLARE @HOLDER INT, @Duration CHAR(12), @StartTime DATETIME;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM (SELECT ID, yourData, MAX(rn)
      FROM (SELECT ID, yourData, split.Part.value('text()[1]', 'VARCHAR(MAX)'), ROW_NUMBER() OVER(PARTITION BY yourData ORDER BY (SELECT NULL))
            FROM (SELECT CAST('<p>' + REPLACE(CAST(yourData AS VARCHAR(MAX)) COLLATE Latin1_General_BIN2,'.','</p><p>') + '</p>' AS XML), 
                  CAST(yourData AS VARCHAR(MAX)), ID
                  FROM #testEnvironment) innerQ(xmlField, yourData, ID) 
            CROSS APPLY innerQ.xmlField.nodes('p') split(Part)
            ) a(ID, yourData,splitData,rn)
      GROUP BY ID, yourData
      ) a(ID, yourData, rn)
WHERE rn = 2;

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for ugly xml split = %s',0,1,@Duration) WITH NOWAIT;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE CHARINDEX('.', yourData, CHARINDEX('.', yourData) + 1) = 0;

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for CHARINDEX = %s',0,1,@Duration) WITH NOWAIT;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE LEN(CAST(yourData AS NVARCHAR(MAX)))-1 = LEN(REPLACE(CAST(yourData AS NVARCHAR(MAX)) COLLATE Latin1_General_BIN2,'.',''));

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for LEN = %s',0,1,@Duration) WITH NOWAIT;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE CHARINDEX('.', yourData COLLATE Latin1_General_BIN2, CHARINDEX('.', yourData COLLATE Latin1_General_BIN2) + 1) = 0;

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for CHARINDEX with COLLATE = %s',0,1,@Duration) WITH NOWAIT;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE PARSENAME(CAST(yourData AS NVARCHAR(MAX)),3) IS NULL
AND PARSENAME(CAST(yourData AS NVARCHAR(MAX)), 2) IS NOT NULL;

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for PARSENAME = %s',0,1,@Duration) WITH NOWAIT;

Duration for ugly xml split = 00:00:47:197
Duration for CHARINDEX = 00:00:07:593
Duration for LEN = 00:00:08:163
Duration for CHARINDEX with COLLATE = 00:00:04:787
Duration for PARSENAME = 00:00:05:193

SELECT *
FROM #testenvironment
WHERE PARSENAME(CAST(yourdata AS NVARCHAR(MAX)),3) IS NULL

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE yourData like '%.%' and yourData not like '%.%.%';

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for LIKE = %s',0,1,@Duration) WITH NOWAIT;

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE yourData COLLATE Latin1_General_BIN2 like '%.%' and yourData COLLATE Latin1_General_BIN2 not like '%.%.%';

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for LIKE = %s',0,1,@Duration) WITH NOWAIT;

Duration for CHARINDEX = 00:00:09:103
Duration for LEN = 00:00:10:790
Duration for CHARINDEX with COLLATE = 00:00:06:507
Duration for PARSENAME = 00:00:07:717
Duration for LIKE = 00:00:10:703
Duration for LIKE with COLLATE = 00:00:06:517

DBCC FREEPROCCACHE WITH NO_INFOMSGS;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;

DECLARE @HOLDER INT, @Duration CHAR(12), @StartTime DATETIME;


SELECT @StartTime = GETDATE();

SELECT @HOLDER = ID
FROM #testEnvironment
WHERE dbo.RegexCLR(ISNULL(yourData,'')) = 1

SELECT @Duration = CONVERT(CHAR(12),GETDATE()-@StartTime,114);
RAISERROR('Duration for SQLCLR = %s',0,1,@Duration) WITH NOWAIT;

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction()]
    public static bool RegexCLR(string input)
    {
        return Regex.IsMatch(input,@"^[^\.]+\.[^\.]+$");                
    }
};

public partial class UserDefinedFunctions
{

    static readonly Regex _regex = new Regex(@"^[^\.]+\.[^\.]+$", RegexOptions.Compiled);
    
    [Microsoft.SqlServer.Server.SqlFunction()]
    public static bool RegexCLR(string input)
    {
        return Regex.IsMatch(input);                
    }
};