Optimizing the stored procedure to process 3 million records

I have designed a stored procedure usign Sql Server 2005 below to compare 3 million records in each of the Profile and Source Table, and update the Source table with records exist in another table (PROFILE_BC) which will also have about 3 million records. I am trying to Optimize this code below. Can you suggest any other method ? I just worried that this will take more than about 6 hours to complete. Can we do the same using DTS ? And ideas how this can be done using DTS. Some suggested that there is a component called, Lookup, Fuzzy Lookup that can be used. Any ideas in optimizing the same are welcome.

USE Database

GO
/****** Object:  StoredProcedure [dbo].[ProcName]    Script Date: 11/13/2010 17:15:04 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE [dbo].[ProcName] 
AS
BEGIN

 SET NOCOUNT ON;

 DECLARE @not_on_ebc_file_xx## char(2);
    SET @not_on_ebc_file_xx## = 35;

 DECLARE @voters_no varchar(18);
    DECLARE @candidate_id char(10);
 DECLARE @perm_disq_temp char(2);
 DECLARE @voters_no_jms varchar(18);


 DECLARE PROFILES_CURSOR CURSOR LOCAL FAST_FORWARD
    FOR SELECT CP.CANDIDATE_ID, CP.VOTERS_NO FROM PROFILE CP INNER JOIN SOURCE SR ON 
 CP.CANDIDATE_ID = SR.CANDIDATE_ID
 WHERE CP.CANDIDATE_ID NOT LIKE 'MA%';


 OPEN 开发者_运维问答PROFILES_CURSOR;
 FETCH NEXT FROM PROFILES_CURSOR 
 INTO @candidate_id, @voters_no;


  WHILE @@FETCH_STATUS = 0
  BEGIN

   SELECT @voters_no_jms = VOTERS_NO FROM PROFILE_BC WHERE VOTERS_NO = @voters_no;  
   SELECT @perm_disq_temp = PERM_DISQ FROM SOURCE WHERE CANDIDATE_ID = @candidate_id;

   IF (@voters_no_jms = @voters_no)  -- record exists in jms_temp table/ebc file
   BEGIN   
    IF (@perm_disq_temp = @not_on_ebc_file_xx##)
    BEGIN
       UPDATE SOURCE SET PERM_DISQ = '' WHERE CANDIDATE_ID = @candidate_id;
    END

    END
    ELSE
    BEGIN
    IF (@perm_disq_temp = '' OR @perm_disq_temp IS NULL) 
    BEGIN
       UPDATE SOURCE SET PERM_DISQ = @not_on_ebc_file_xx##  WHERE CANDIDATE_ID = @candidate_id;
    END   
    END

   SET @voters_no_jms = '';

   FETCH NEXT FROM PROFILES_CURSOR INTO @candidate_id, @voters_no;

  END 

 CLOSE PROFILES_CURSOR;
 DEALLOCATE PROFILES_CURSOR;

END

you should always try to avoid using cursors if you have performance on mind. Instead of using a cursor you could do this. Try to think in terms of sets when dealing with SQL. I commented out the update part of the query and added a select so that you can see the data.

BEGIN TRANSACTION

DECLARE @not_on_ebc_file_xx## char(2); 
SET @not_on_ebc_file_xx## = 35;

--UPDATE SR
--SET       PERM_DISQ = 
--          CASE WHEN NOT PROFILE_BC.VOTERS_NO IS NULL THEN
--                  CASE WHEN PERM_DISQ.PERM_DISQ = @not_on_ebc_file_xx## THEN '' 
--                      ELSE PERM_DISQ.PERM_DISQ 
--                  END
--              WHEN PERM_DISQ.PERM_DISQ = '' OR PERM_DISQ   IS NULL THEN @not_on_ebc_file_xx##
--              ELSE  PERM_DISQ.PERM_DISQ
--          END
SELECT  CASE WHEN NOT PROFILE_BC.VOTERS_NO IS NULL THEN
                    CASE WHEN PERM_DISQ.PERM_DISQ = @not_on_ebc_file_xx## THEN '' 
                        ELSE PERM_DISQ.PERM_DISQ 
                    END
                WHEN PERM_DISQ.PERM_DISQ = '' OR PERM_DISQ   IS NULL THEN @not_on_ebc_file_xx##
                ELSE  PERM_DISQ.PERM_DISQ
            END AS PERM_DISQ
FROM    PROFILE CP
        INNER JOIN SOURCE SR
            ON CP.CANDIDATE_ID = SR.CANDID_ID
        LEFT JOIN PROFILE_BC
            ON CP.VOTERS_NO = PROFILE_BC.VOTERS_NO
        LEFT JOIN SOURCE PERM_DISQ
            ON CP.CANDIDATE_ID = PERM_DISQ.CANDIDATE_ID
WHERE   CP.CANDIDATE_ID NOT LIKE 'MA%';


ROLLBACK TRANSACTION;

uncomment the update and set statement and comment out the select statement to update