T-SQL Query Optimization

select
    path as EntryPage,
    count(Path) as [Count]
from
    (
    	/* Sub-query 1 */
    	select
    		pv2.path
    	from
    		pageviews pv2
    			inner join
    				(
    					/* Sub-query 2 */
    					select
    						pv1.sessionid,
    						min(pv1.created) as created
    					from
    						pageviews pv1
    							inner join Sessions s1 on pv1.SessionID = s1.SessionID
    							inner join Visitors v1 on s1.VisitorID = v1.VisitorID
    					where
    						pv1.Domain = isnull(@Domain, pv1.Domain) and
    						v1.Campaign = @Campaign
    					group by
    						pv1.sessionid
    				) t1 on pv2.sessionid = t1.sessionid and pv2.created = t1.created
    ) t2
group by
    Path;

select
    pv.Path,
    count(*)
from
    PageViews pv
    	inner join Sessions s on pv.SessionID = s.SessionID
    		and pv.PageViewID = s.ExitPage
    	inner join Visitors v on s.VisitorID = v.VisitorID
where
    (
        @Domain is null or
        pv.Domain = @Domain
    ) and
    v.Campaign = @Campaign
group by pv.Path;

where pv1.Domain = isnull(@Domain, pv1.Domain)

SELECT
    sessionid,
    MIN(created) AS created
FROM
    pageviews pv
JOIN
    visitors v ON pv.visitorid = v.visitorid
WHERE
    v.campaign = @Campaign
GROUP BY
    sessionid

SELECT
    campaignid,
    sessionid,
    pv.path
FROM
    pageviews pv
JOIN
    visitors v ON pv.visitorid = v.visitorid
WHERE
    v.campaign = @Campaign
    AND NOT EXISTS (
        SELECT 1 FROM pageviews
        WHERE sessionid = pv.sessionid
        AND created < pv.created
    )

where
   (@Domain is null or pv1.Domain = @Domain) and
   v1.Campaign = @Campaign

create index idx2 on [PageViews]([SessionID], Domain, Created, Path)