在分析SQL性能的时候，经常需要确定资源消耗多的SQL，总结如下：

1 查看值得怀疑的SQL
select substr(to_char(s.pct,'99.00'),2)||'%'load,

       s.executions executes,

       p.sql_text

from(select address,

            disk_reads,

            executions,

            pct,

            rank() over(order by disk_reads desc) ranking

         from(select address,

                     disk_reads,

                     executions,

                     100*ratio_to_report(disk_reads) over() pct

                 from sys.v_$sql

                where command_type!=47)

        where disk_reads>50*executions) s,

       sys.v_$sqltext p

where s.ranking10000

order by disk_reads desc;

3 查看逻辑读多的SQL
select*

from(select buffer_gets, sql_text

     from v$sqlarea

     where buffer_gets>500000

     order by buffer_gets desc)

where rownum