Question

I have a SQL Server query as:

SELECT top 1 vConsentInfo  FROM 
(           
            SELECT cons.vConsentInfo,cons.dTimeStamp ,logs.iPartnerProfileID 
            FROM H_OutMessageLog logs INNER JOIN H_OutMessageConsent cons on cons.iOutMessageQID = logs.iOutQueueID 
                WHERE logs.iPatID = 65686 and logs.iPracID = 4
        UNION  
            SELECT cons.vConsentInfo,cons.dTimeStamp,Q.iPartnerProfileID 
            FROM H_OutMessageQueue Q INNER JOIN H_OutMessageConsent cons on cons.iOutMessageQID = Q.iOutQueueID 
                WHERE Q.iPatID = 65686 and Q.iPracID = 4
) A 
WHERE A.iPartnerProfileID = Prof.IPartnerProfileID
Order BY dTimeStamp DESC

The table works as : a record get inserted into H_OutMessageQueue at the begining; then its inserted into H_OutMessageConsent…
Now there is a seperate worker process that processes records from H_OutMessageQueue and log them into H_OutMessageLog….

Can I get rid of this UNION thing ? Please note that this is a sub Query of a larger CTE query.

Answer 1

Yes, but it may not be better. You’ll have to work this into your bigger query

SELECT TOP 1 
    cons.vConsentInfo,
    ISNULL(logs.iPartnerProfileID , Q.iPartnerProfileID) AS iPartnerProfileID
FROM 
    H_OutMessageConsent cons 
    LEFT JOIN
    H_OutMessageLog logs ON cons.iOutMessageQID = logs.iOutQueueID AND 
                               logs.iPatID = 65686 and logs.iPracID = 4
    LEFT JOIN
    H_OutMessageQueue Q ON cons.iOutMessageQID = Q.iOutQueueID  AND
                               Q.iPatID = 65686 and Q.iPracID = 4
WHERE
    ISNULL(logs.iPartnerProfileID , Q.iPartnerProfileID) IS NOT NULL
ORDER BY 
    cons.dTimeStamp DESC