Optimizing Stored Procedure

Hi all,

I have have this stored procedure which gets records from the SQL Server database which are then displayed on a web page. In the second part of the stored procedure, it has the exact same SELECT statement as in first part but it just returns the total duration. I have noticed that when the number of records is very large, the CPU time goes up to 100% for a second (while its fetching data) and then goes back to normal.

Please guide me to what optimizations can be done to this procedure. CREATE Procedure GetCDR_LikeTollFree
(
@theDuration int = null, --to find duration more than theDuration
@totalDuration bigint = null, --to find the total duration for the result set
@callerName varchar(255) = null,
@callingPartyNumber varchar(255) = null,
@originalCalledPartyNumber varchar(255) = null,
@finalCalledPartyNumber varchar(255) = null,
@dateTimeConnect datetime = null,
@dateTimeDisconnect datetime = null,
@clientMatterCode varchar(255) = null
)

AS
BEGIN
SELECT callingPartyNumber, AlertingName, originalCalledPartyNumber, finalCalledPartyNumber,
dateTimeConnect,
dateTimeDisconnect,
CONVERT(char(8), DATEADD(second, duration, '0:00:00'), 108) AS duration,
clientMatterCode


FROM CDR1.dbo.CallDetailRecord t1
LEFT JOIN CDR2.dbo.NumPlan t2 ON t1.callingPartyNumber=t2.DNorPattern

WHERE
(t1.callingPartyNumber LIKE ISNULL(@callingPartyNumber, t1.callingPartyNumber) + '%') AND
(t1.originalCalledPartyNumber LIKE ISNULL(@originalCalledPartyNumber, t1.originalCalledPartyNumber) + '%') AND
(t1.finalCalledPartyNumber LIKE ISNULL(@finalCalledPartyNumber, t1.finalCalledPartyNumber) + '%') AND
(t1.clientMatterCode LIKE ISNULL(@clientMatterCode, t1.clientMatterCode) + '%') AND
(@callerName is NULL OR t2.AlertingName LIKE '%' + @callerName + '%') AND
(t1.duration >= @theDuration) AND
((t1.datetimeConnect) >= ISNULL(convert(bigint,
datediff(ss, '01-01-1970 00:00:00', @dateTimeConnect)), t1.datetimeConnect)) AND
((t1.dateTimeDisconnect) <= ISNULL(convert(bigint,
datediff(ss, '01-01-1970 00:00:00', @dateTimeDisconnect)), t1.dateTimeDisconnect))


SET @totalDuration = (SELECT SUM(duration)

FROM CDR1.dbo.CallDetailRecord t1
LEFT JOIN CDR2.dbo.NumPlan t2 ON t1.callingPartyNumber=t2.DNorPattern


WHERE

(callingPartyNumber LIKE ISNULL(@callingPartyNumber, callingPartyNumber) + '%') AND
(originalCalledPartyNumber LIKE ISNULL(@originalCalledPartyNumber, originalCalledPartyNumber) + '%') AND
(finalCalledPartyNumber LIKE ISNULL(@finalCalledPartyNumber, finalCalledPartyNumber) + '%') AND
(clientMatterCode LIKE ISNULL(@clientMatterCode, clientMatterCode) + '%') AND
(@callerName is NULL OR t2.AlertingName LIKE '%' + @callerName + '%') AND
(duration >= @theDuration) AND
((datetimeConnect) >= ISNULL(convert(bigint,
datediff(ss, '01-01-1970 00:00:00', @dateTimeConnect)), datetimeConnect)) AND
((dateTimeDisconnect) <= ISNULL(convert(bigint,
datediff(ss, '01-01-1970 00:00:00', @dateTimeDisconnect)), dateTimeDisconnect))

)

RETURN @totalDuration

END
GO