I have a stored procedure on a busy database which constantly come out top in the list of expensive queries (by some way). The query is very simple, it takes a single parameter (@ID, int) which is the primary key of the table, and selects the record that matches that ID. The primary key is an identity field with a clustered index, so I am stumped as to how to optimise this any further?

The query is as follows

CREATE PROCEDURE [dbo].[P_Call_Get]

    @ID int = null

AS

    select ID,
        AppID,
        AgentID,
        AgentLogin,
        Ext,
        VDN,
        VDNName,
        Skill,
        SkillName,
        CallFrom,
        TelNoFrom,
        ParentCallID,
        CallStart,
        ACWStart,
        CallEnd,
        Outcome,
        StageID,
        TxTo,
        TxSuccess,
        ServiceID,
        DiallerID,
        CRC,
        TSCallID,
        CallDirection,
        [Manual],
        CallBackAgent,
        CallBackDateTime,
        Notes
    from P_Call
    where (ID = @ID or @ID is null)

Not sure the best way to post the execution plan - all it shows is that 100% of the operation is taken up by the clustered index scan