使用SQL Tuning Advisor(STA)为sql提供优化建议
在Oracle10g之前，优化SQL是个比较费力的技术活，不停的分析执行计划，加hint，分析统计信息等等。
在10g中，Oracle推出了自己的SQL优化辅助工具: SQL优化器(SQL Tuning Advisor ：STA)，它可以给出优化建议。
使用STA一定要保证优化器是CBO模式下。
一 创建优化任务
可以通过传入文本来获取相应的优化建议，也可以通过sql_id方式获取。
1.1 传入文本方式
DECLARE
my_task_name VARCHAR2(30);
my_sqltext CLOB;
BEGIN
my_sqltext := 'select count(*) from bigtab a, smalltab b where a.object_name=b.table_name';
my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK(
sql_text => my_sqltext,
user_name => 'SCOTT', -- 表示该语句由哪个用户执行，注意用户名须大写
scope => 'COMPREHENSIVE',
time_limit => 60,
task_name => 'tuning_sql_test',
description => 'Task to tune a query on a specified table');
DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name => 'tuning_sql_test');
END;
/1.2 传入sql_id方式
#根据sql文本获取sql_id：
select sql_id,sql_text from v$sqlarea where sql_text like '%bigtab%'
#传入sql_id
DECLARE
my_task_name VARCHAR2(30);
sql_id VARCHAR2(30);
BEGIN
sql_id := '&sqlid';
my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK
(sql_id=> sql_id,
scope => 'comprehensive',
time_limit=>60,
task_name=>'tuning_sql_test',
description => 'Tuning Task');
DBMS_SQLTUNE.EXECUTE_TUNING_TASK('tuning_sql_test');
END;
/二 执行优化任务
SQL> exec dbms_sqltune.execute_tuning_task('tuning_sql_test');
--检查优化任务的状态
SYS@PROD1>SELECT task_name,status FROM USER_ADVISOR_TASKS WHERE task_name ='tuning_sql_test';
TASK_NAME STATUS
------------------------------ -----------
tuning_sql_test COMPLETED
三 查看优化建议
SET LONG 999999
set serveroutput on size 999999
SET LINESIZE 1000
SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK( 'tuning_sql_test') from DUAL;
优化建议如下：
……
The execution plan of this statement can be improved by creating one or more
indices.
Recommendation (estimated benefit: 99.57%)
------------------------------------------
- Consider running the Access Advisor to improve the physical schema design
or creating the recommended index.
DBMS_SQLTUNE.REPORT_TUNING_TASK('TUNING_SQL_TEST')
--------------------------------------------------------------------------------
create index SCOTT.IDX$$_0E4C0001 on SCOTT.BIGTAB("OBJECT_NAME");
- Consider running the Access Advisor to improve the physical schema design
or creating the recommended index.
create index SCOTT.IDX$$_0E4C0002 on SCOTT.SMALLTAB("TABLE_NAME");
……四 删除优化任务
exec dbms_sqltune.drop_tuning_task('tuning_sql_test');
--本篇文章主要参考自https://blog.csdn.net/tianlesoftware/article/details/5630888