有时候执行的oracle，sql语句要查看下性能情况，可以用这个进行下简单计算和统计

--http://www.cnblogs.com/Invokerr/p/7084786.html
SELECT  ELAPSED_TIME,LAST_ACTIVE_TIME,EXECUTIONS , DISK_READS, BUFFER_GETS, 
ROUND((BUFFER_GETS-DISK_READS)/BUFFER_GETS,2) Hit_radio, 
ROUND(DISK_READS/EXECUTIONS,2) Reads_per_run, SQL_TEXT 
FROM  V$SQLAREA 
WHERE  EXECUTIONS>0 
AND  BUFFER_GETS > 0 
AND  (BUFFER_GETS-DISK_READS)/BUFFER_GETS < 0.8 
and SQL_TEXT like '%htjs%'
ORDER BY  5 DESC;