IF (OBJECT_ID('tempdb..#Block') IS NOT NULL)
DROP TABLE #Block

IF (OBJECT_ID('tempdb..#SampleNumbers') IS NOT NULL)
DROP TABLE #SampleNumbers

CREATE TABLE #Block (N CHAR(3) PRIMARY KEY WITH(FILLFACTOR = 100), isProcessed BIT DEFAULT(0))
CREATE TABLE #SampleNumbers (Block CHAR(7) PRIMARY KEY)

INSERT INTO #Block(N)
SELECT '000' AS N UNION ALL
SELECT TOP 999 RIGHT ('000' + CAST( ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS VARCHAR),3)
FROM sys.all_columns;

INSERT INTO #SampleNumbers
SELECT *
  FROM (VALUES ('1234567'),('2345678'),('3456789'),('4567890'))x(TopLevel)

--INSERT INTO MyTable                  
SELECT Block + N
  FROM #SampleNumbers
 CROSS JOIN #Block

IF (OBJECT_ID('tempdb..#tempSample') IS NOT NULL)
DROP TABLE #tempSample

CREATE TABLE #tempSample (Block CHAR(7))
CREATE CLUSTERED INDEX uix_tmpSampleIndex ON #tempSample(Block)

DECLARE @Count INT = 1

WHILE @Count > 0
BEGIN
	BEGIN TRY
		BEGIN TRANSACTION
		
		UPDATE TOP (500) a SET isProcessed = 1
		OUTPUT inserted.Block INTO #tempSample
			FROM #SampleNumbers a
		 WHERE isProcessed = 0

		SET @Count = @@ROWCOUNT

		--INSERT INTO MyTable (MyCol)
		SELECT Block + N
		   FROM #tempSample
		CROSS APPLY #Num
		
		COMMIT TRANSACTION
	END TRY
	BEGIN CATCH
		ROLLBACK TRANSACTION
	END CATCH
	
TRUNCATE TABLE #tempSample
WAITFOR DELAY '00:00:01'

END
DROP TABLE #tempSample