Question

I have following piece of sql, whilst it is functioning as expected, it is a bit slow to return results (by slow I’m talking about 10 seconds to return 1000 results from a months date range). Is it possible for it to be made more efficient and/or quicker? Just to add these are the following indexes I have on the tables:-

• RecordID – Primary Key Unique Clustered
• Department – Non clustered
• Direction – Non clustered
• LocalCallGroup – Non clustered
• ServiceProvider – Non clustered
• StartTime- Non clustered
• UserID- Non clustered
• UserLocalStartTime – Non clustered
• UserLocalTimeOffset – Non clustered
• UserNumber – Non clustered

Declaration of variables here, removed for post

    SET @TerminatingSQL = '
    SELECT 
        UserNumber, 
        ImageDirection = ''in'', 
        CallingNumber = CASE WHEN callingnumber IN(''Unavailable'',''Unknown'',''+44anonymous@10.81.253.12'',''0anonymous@10.81.253.12'') THEN ''Anonymous'' ELSE callingnumber END,
        CalledNumber,
        StartTime = dateadd(ms,(-datepart(ms,(startTime))),(startTime)),
        AnswerTime = dateadd(ms,(-datepart(ms,(answerTime))),(answerTime)),
        ReleaseTime =  dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)),         
        CallDuration =  dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)) - dateadd(ms,(-datepart(ms,(answerTime))),(answerTime)),
        TotalDuration = dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)) - dateadd(ms,(-datepart(ms,(startTime))),(startTime)),
        terminationCause,
        recordID
    FROM
        dbo.TABLEA' + @Table +'
    WHERE
        serviceProvider IN ( SELECT serviceProvider FROM ccNumbers WHERE CRMID = ' + CONVERT(VARCHAR(10),@CrmId,103) + ')
        AND startTime between ''' + CONVERT(VARCHAR(10),@Fromdate,112) + ''' AND ''' + CONVERT(VARCHAR(10), @ToDate, 112) + '''
        AND Direction = ''terminating''
        AND (Department = ''' + @Department + ''' OR ''' + @Department + ''' = ''ALL'')
        AND (userid = ''' + @Userid + ''' OR ''' + @Userid + ''' = ''ALL'')'

    SET @OriginatingSQL = '
    SELECT 
        UserNumber, 
        ImageDirection = ''out'', 
        CallingNumber = CASE WHEN callingnumber IN(''Unavailable'',''Unknown'',''+44anonymous@10.81.253.12'',''0anonymous@10.81.253.12'') THEN ''Anonymous'' ELSE callingnumber END,
        CalledNumber,
        StartTime = dateadd(ms,(-datepart(ms,(startTime))),(startTime)),
        AnswerTime = dateadd(ms,(-datepart(ms,(answerTime))),(answerTime)),
        ReleaseTime =  dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)),         
        CallDuration =  dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)) - dateadd(ms,(-datepart(ms,(answerTime))),(answerTime)),
        TotalDuration = dateadd(ms,(-datepart(ms,(releaseTime))),(releaseTime)) - dateadd(ms,(-datepart(ms,(startTime))),(startTime)),
        terminationCause,
        recordID
    FROM
        dbo.TABLEA' + @Table +'
    WHERE
        serviceProvider IN ( SELECT serviceProvider FROM ccNumbers WHERE CRMID = ' + CONVERT(VARCHAR(10),@CrmId,103) + ')
        AND startTime between ''' + CONVERT(VARCHAR(10),@Fromdate,112) + ''' AND ''' + CONVERT(VARCHAR(10), @ToDate, 112) + '''
        AND Direction = ''originating''
        AND (Department = ''' + @Department + ''' OR ''' + @Department + ''' = ''ALL'')
        AND (userid = ''' + @Userid + ''' OR ''' + @Userid + ''' = ''ALL'')'

    SET @MainSelectSQL = @TerminatingSQL + ' Union '  + @OriginatingSQL

    SET @MainSQL = 'SELECT TOP (' + @PageSize + ') 
        [t1].CalledNumber,
        [t1].CallingNumber,
        [t1].UserNumber, 
        [t1].StartTime,
        [t1].AnswerTime,
        [t1].ReleaseTime,
        [t1].ImageDirection,
        [t1].CallDuration,
        [t1].TotalDuration,
        [t1].TerminationCause
    FROM (
        SELECT ROW_NUMBER() OVER (
            ORDER BY [t0].startTime) as [row_number], 
            [t0].CalledNumber,
            [t0].CallingNumber,
            [t0].UserNumber,
            [t0].StartTime,
            [t0].AnswerTime,
            [t0].ReleaseTime,
            [t0].ImageDirection,
            [t0].CallDuration,
            [t0].TotalDuration,
            [t0].TerminationCause
        FROM
            (' + @MainSelectSQL + ')  AS [t0] 
          )  AS [t1]

    WHERE [t1].[row_number] > ' + @Page + ' * ' + @PageSize +';'

    EXEC (@MainSQL)

-- Work out the total number of rows, but don't bother if we have the number already (i.e. when they keep the same parameters and just click paging.

IF  (@CurrentCount IS NULL)
    BEGIN
        DECLARE @TotalCountSQL nvarchar(4000)
        DECLARE @ParameterList NVARCHAR(4000)   

        SET @ParameterList = '@TotalCount int OUTPUT'
        SET @TotalCountSQL = 'SELECT @TotalCount = COUNT(recordId) FROM (' + @MainSelectSQL + ') as a'

        EXEC SP_EXECUTESQL @TotalCountSQL,@ParameterList,@TotalCount=@TotalCount OUTPUT
    END
ELSE
    BEGIN
        SET @TotalCount = @CurrentCount;
    END
END

Answer 1

Things to improve

• UNION ALL will remove an implied DISTINCT. The ImageDirection column ensures that there is no overlap anyway, so UNION adds an extra step in the plan

• Where you have ROW_NUMBER(), add COUNT(*) OVER () to get the total record count. This removes the need for the 2nd call

Thoughts:

• Do you have dynamic table names that requires such ugly concatenation?
  Except for that, I see no need for dynamic SQL

• Consider using a temp table to stage results to simplify complexity