Question

I have a select script that runs 3 times a day in a 2005 SQL Server installation, a few times the return table has contained expected number of rows but without any values. The integer and date fields have zeros and the others are simply blank.

Since the problem occurs very rarely there is no way to supervise the database when the script runs and haven’t been able to replicate the issue. My thought is that some other update in the database is causing the problem. Does anyone know about this problem?

Here is the script

SELECT DISTINCT
    URL.Line, 
    RTrim(URL.DescriptionNote) AS [DescriptionNote], 
    SA1.Name AS [Name1], 
    SP1.Designation AS [Designation1], 
    SA2.Name [Name2], 
    SP2.Designation AS  [Designation2],
    RL.DistanceMeters,
    dbo.RouteLinkTransportModeDesc(URL.TransportModeTypeNumber) AS TransportMode, 
    URL.THM,
    URL.FirstWorkedDate,
    URL.LastWorkedDate
FROM #RequiredRouteLink URL
    INNER JOIN StopPoint AS SP1
        ON SP1.JourneyPatternPointGid = URL.StartsAtPointGid
    INNER JOIN StopArea AS SA1
        ON SP1.IsPartOfStopAreaVersionId = SA1.VersionId
    INNER JOIN StopPoint AS SP2
        ON SP2.JourneyPatternPointGid = URL.EndsAtPointGid
    INNER JOIN StopArea AS SA2
        ON SP2.IsPartOfStopAreaVersionId = SA2.VersionId
    LEFT JOIN verRouteLink AS RL 
        ON RL.StartsAtPointGid = URL.StartsAtPointGid 
    AND RL.EndsAtPointGid = URL.EndsAtPointGid 
    AND URL.TransportModeTypeNumber = RL.TransportModeTypeNumber 
WHERE URL.StartsAtPointGid <> URL.EndsAtPointGid 
    AND (RL.EndsAtPointGid IS NULL OR RL.DistanceMeters = 0 OR RL.DistanceMeters IS NULL)
    AND RL.[DeletedDateTime] IS NULL
ORDER BY FirstWorkedDate, THM, TransportMode, Line, DescriptionNote

Answer 1

I’m sure it is a data issue. The reason you are getting blank fields is most likely the LEFT JOIN.

You have 4 INNER JOINs, any one of which could cause you to have an empty result set. If one or more of those don’t find a match, you have no results.

However, your LEFT JOIN means you will at least get the list of URL.Line, which is why you had the expected number of rows most likely.