Tips on how to optimize and SQL Query

Hi i wounder if anyone has any tips on how i should optimize this Query?

DECLARE @RowsToProcess  int
DECLARE @CurrentRow     int
DECLARE @SelectCol1     int
declare @dateNow datetime
declare @macAdress varchar(100);
declare @port varchar(100);
declare @switchName varchar(100);
declare @vlan varchar(100);

declare @changedmacAdress varchar(100);
declare @changedvlan varchar(100);

DECLARE @table1 TABLE (RowID int not null primary key identity(1,1), col1 int,
 [macAdress] [varchar](255) NULL,
 [portName] [varchar](255) NULL,
 [switchName] [varchar](255) NULL,
 [vlan] [varchar](255) NULL)  

INSERT into @table1 SELECT id,macAdress,portName,switchName,vlan FROM ForwardDatabase

SET @RowsToProcess=@@ROWCOUNT

select @dateNow = getdate()

SET @CurrentRow=0  
WHILE @CurrentRow<@RowsToProcess
 BEGIN
  SET @CurrentRow=@CurrentRow+1
     SET @macAdress = null;
 SET @port = null;
 SET @switchName = null;
 SET @vlan = null;

     SET @changedmacAdress = null;
     SET @changedvlan = null;


  SELECT 
    @SelectCol1=col1,@macAdress=macAdress,@port=portName,@switchName=switchName,@vlan=vlan
    FROM @table1
    WHERE RowID=@CurrentRow


   select @macAdress=macAdress,@port=portName,@switchName=switchName,@vlan=vlan from @table1 where RowID = @SelectCol1

   select @changedmacAdress=macAdress,@changedvlan=vlan from HistoryForwardDatabase where macAdress= @m开发者_如何学PythonacAdress and vlan = @vlan and portName = @port and switchname=@switchName and changeDate = (select MAX(changedate) from HistoryForwardDatabase  where portName = @port and switchname=@switchName)

   IF(@changedmacAdress is null and @changedvlan is null)
    begin       
    insert into HistoryForwardDatabase (macAdress,portname,changeDate,switchName,vlan) select macAdress,portName,@dateNow,switchName,vlan from @table1 where portName = @port and switchName =@switchName
    end
END

This query might do the trick for you:

INSERT INTO HistoryForwardDatabase (macAdress, portname, changeDate, switchName, vlan)
SELECT f.macAdress, f.portName, h.changeDate, f.switchName, f.vlan 
FROM ForwardDatabase AS f
LEFT JOIN HistoryForwardDatabase AS h
    ON f.macAdress= h.macAdress 
    AND f.vlan = h.vlan 
    AND f.portName = h.portName
    AND f.switchname= h.switchName 
    AND h.changeDate = (SELECT MAX(h2.changedate) 
        FROM HistoryForwardDatabase h2 
        WHERE h2.portName = h.portName 
        AND h2.switchname h.switchName)
WHERE h.macAddress IS NULL AND h.vlan IS NULL

Optimization is very abstract term. In case you need optimize speed try use Execution plan.