Oracle sql语句 exits优化
SELECT SUM (
(SELECT SUM (pvarticlecount)
FROM hit_node_articlecount
WHERE ismaster = 1
AND articleid = pr.articleid
AND stattime BETWEEN TO_DATE ('2014-06-29', 'yyyy-mm-dd')
AND TO_DATE ('2014-07-29', 'yyyy-mm-dd')))
pvcount,
firstpub
FROM releaselib pr
WHERE EXISTS
(SELECT ui.loginname
FROM userinfo ui, userrole ur
WHERE ( ( ur.siteid = 2
AND pr.inputer = ur.loginname
AND ur.loginname = ui.loginname)
OR ui.userlevel = 20))
AND pr.publishstate = 2
GROUP BY pr.firstpub
使用了exists,因为releaselib表中的数据比较多, 这个sql查询效率太慢,该怎么优化改进,求高手指导