Join tables where the table name changes every day I need some help in figuring out how to join tables to my query.  The table names change every day as the date is used in the table name and older tables are dropped as they are no longer needed.

My query looks for "scans" that have data in the database and are in the process of being processed (for a lack of a better word).

My current query is:

USE RetinaCSDatabase
SELECT S.ScanID [Scan ID], S.PolicyName [Scan], DATEADD(hh, +2, S.StartTime) [Scan Start], A.AssetName [Scanner], COUNT(AIPS.AssetIPID) [Hosts], S.TransactionGroup [Transaction Group ID]
FROM Scan S (NOLOCK)
LEFT JOIN Scanner SC (NOLOCK) ON S.ScannerID = SC.ScannerID
LEFT JOIN Asset A (NOLOCK) ON SC.AssetID = A.AssetID
LEFT JOIN Asset_IP_Scan AIPS (NOLOCK) ON S.ScanID = AIPS.ScanID
WHERE S.ProcessStatus &lt; 2
GROUP BY S.ScanID, S.PolicyName, S.StartTime, A.AssetName, S.TransactionGroup
ORDER BY S.StartTime ASC, S.PolicyName ASC, A.AssetName ASC


What I need to join is the table(s) with the data still requiring processing.  Those tables start with the name "evt_scan_" and then the date.  So, a full table name would be "evt_scan_20171222" for example.  The data for a scan performed on the 22nd of December 2017 will have data in the table "evt_scan_20171222" and possibly in the following days table, "evt_scan_20171223".  So, I need my query first to check if the table exists and then join it to do a count and also to check if the following days table exists, join it to do another count and add up the 2 counts to show the outstanding records requiring processing.

If the table names were static I would join them with this query:

LEFT JOIN evt_scan_20171222 evt1 ON S.TransactionGroup = evt1.evtTransactionGroup


It would also require a WHERE statement returning only records where evtStatus = 0.

Thanks
Use a synonym.

USE YourDatabaseName;
DECLARE @sql nvarchar(max) = N'CREATE SYNONYM
  dbo.EventScan FOR dbo.evt_scan_'
  + CONVERT(CHAR(8), GETDATE(), 112);
EXEC sys.sp_executesql @sql;


Then your code can always reference dbo.EventScan.

Now, schedule a job to run every night at 12:00:01 AM (or create a DDL trigger on table creation and when the new table name matches the expected pattern, or put code in whatever creates those new tables each day) that does this:

USE YourDatabaseName;
DROP SYNONYM dbo.EventScan;
— repeat code from above