找出低效SQL

--用下列SQL工具找出低效SQL

SELECT 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
ORDER BY 4 DESC;