I'm trying to get different values from my While loop I seem to be getting the same value printed 3 times - tsql

Question

I've tried to use a While Loop and I seem to be getting the same value printed 3 times I need to have different values printed.
DECLARE #Counter INT
SET #Counter = 1
WHILE ( #Counter <= (SELECT COUNT(*) FROM #TempTable_Log))
--To handle gaps in the looping column value
BEGIN PRINT #Counter
SELECT #LogbackupFile = physical_device_name, #LogBackupSQL = #LogbackupFile
FROM #TempTable_log
WHERE backup_finish_date > ISNULL(#DiffDate, #FullBackupDate)
AND backup_finish_date > #FullBackupDate
AND backup_finish_date <= #RestoreDate
SET #Counter = #Counter + 1
SET #LogBackupSQL = 'RESTORE LOG ' + #DatabaseNameCopy + ' FROM DISK
= ''' + #LogbackupFile + ''' WITH FILE = 1, NOUNLOAD, STATS = 5,'
PRINT #LogBackupSQL end END
Result
(3 rows affected)
1
RESTORE LOG ns_lots_of_vlfs_copy FROM DISK = 'C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_03_10022023.trn' WITH FILE = 1, NOUNLOAD, STATS = 5,
2
RESTORE LOG ns_lots_of_vlfs_copy FROM DISK = 'C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_03_10022023.trn' WITH FILE = 1, NOUNLOAD, STATS = 5,
3
RESTORE LOG ns_lots_of_vlfs_copy FROM DISK = 'C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_03_10022023.trn' WITH FILE = 1, NOUNLOAD, STATS = 5,
Expected Result
C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_03_10022023.trn
C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_02_10022023.trn
C:\Program Files\Microsoft SQL Server\MSSQL15.KUSHALRATTU\MSSQL\Backup\ns_lots_of_vlfs_tran_01_10022023.trn

Answer 1

Firstly, the reason for the behaviour is because each iteration of your loop you are doing the same thing. In your SQL you are assigning an arbitrary value to you variable #LogbackupFile and as this value is from a temporary table it has a high likelihood that that arbitrary value will be the same value every time.
Effectively you are doing something like this:
CREATE TABLE #Temp (I int)
INSERT INTO #Temp (I)
VALUES(1),(3),(2); --Intentionally in an "odd" order
GO
DECLARE #C int = 1;
DECLARE #I int;
WHILE #C <= (SELECT COUNT(*) FROM #Temp) BEGIN
--Assign an arbitrary value to #i
SELECT #I = I
FROM #Temp;
PRINT #I;
SET #C = #C + 1;
END;
GO
DROP TABLE #Temp;
This, very likely, returns the value 2 3 times.
In truth, I'm not sure why you want to PRINT these values. Why not just SELECT the dataset you need? This will return multiple rows with a separate RESTORE LOG on each line:
SELECT 'RESTORE LOG ' + #DatabaseNameCopy + ' FROM DISK = ''' + physical_device_name + ''' WITH FILE = 1, NOUNLOAD, STATS = 5,'
FROM #TempTable_log
WHERE backup_finish_date > ISNULL(#DiffDate, #FullBackupDate)
AND backup_finish_date > #FullBackupDate
AND backup_finish_date <= #RestoreDate
ORDER BY backup_finish_date;
If you must PRINT it, you could use string aggregation, assuming that the total value will be less than 8,000 bytes:
DECLARE #Restore nvarchar(4000),
#CRLF nchar(2) = NCHAR(13) + NCHAR(10);
SELECT #Restore = STRING_AGG('RESTORE LOG ' + #DatabaseNameCopy + ' FROM DISK = ''' + physical_device_name + ''' WITH FILE = 1, NOUNLOAD, STATS = 5,',#CRLF) WITHIN GROUP (ORDER BY backup_finish_date)
FROM #TempTable_log
WHERE backup_finish_date > ISNULL(#DiffDate, #FullBackupDate)
AND backup_finish_date > #FullBackupDate
AND backup_finish_date <= #RestoreDate;
PRINT #Restore;
If you must use a WHILE lop (which I suggest against), you need to ensure that you assign a different value each iteration. As I can't see your data, and thus don't know what it in the table, one method would be to DELETE the "first" row each iteration, so that you get a different row each time. This assumes that backup_finish_date and physical_device_name are npth unique values.
DECLARE #Counter int;
SET #Counter = 1;
WHILE (#Counter <= (SELECT COUNT(*)FROM #TempTable_Log))
BEGIN
PRINT #Counter;
SELECT TOP (1)
#LogbackupFile = physical_device_name,
#LogBackupSQL = #LogbackupFile
FROM #TempTable_log
WHERE backup_finish_date > ISNULL(#DiffDate, #FullBackupDate)
AND backup_finish_date > #FullBackupDate
AND backup_finish_date <= #RestoreDate
ORDER BY backup_finish_date;
SET #Counter = #Counter; --I assume this should start at 1, not 2?
SET #LogBackupSQL = 'RESTORE LOG ' + #DatabaseNameCopy + ' FROM DISK = ''' + #LogbackupFile + ''' WITH FILE = 1, NOUNLOAD, STATS = 5,';
PRINT #LogBackupSQL;
DELETE FROM #TempTable_log
WHERE physical_device_name = #LogbackupFile;
END;