性能优化之查看bad sql语句
在oracle性能优化过程中,查出bad sql(即sql语句有问题)并根据查询结果来优化语句达到优化性能的目的的手段是很普遍的,下面是一些查询bad sql的sql语句,与大家分享!
-- 逻辑读多的SQL
select * from (select buffer_gets, sql_text
from v$sqlarea
where buffer_gets > 500000
order by buffer_gets desc) where rownum<=30;
-- 执行次数多的SQL
select sql_text,executions from
(select sql_text,executions from v$sqlarea order by executions desc)
where rownum<81;
-- 读硬盘多的SQL
select sql_text,disk_reads from
(select sql_text,disk_reads from v$sqlarea order by disk_reads desc)
where rownum<21;
-- 排序多的SQL
select sql_text,sorts from
(select sql_text,sorts from v$sqlarea order by sorts desc)
where rownum<21;
--分析的次数太多,执行的次数太少,要用绑变量的方法来写sql
set pagesize 600;
set linesize 120;
select substr(sql_text,1,80) "sql", count(*), sum(executions) "totexecs"
from v$sqlarea
where executions < 5
group by substr(sql_text,1,80)
having count(*) > 30
order by 2;
posted on 2009-08-25 15:42 xuanyuanvista 阅读(291) 评论(0) 编辑 收藏 举报