oracle查询执行计划的方法有哪些
这篇文章主要介绍"oracle查询执行计划的方法有哪些"，在日常操作中，相信很多人在oracle查询执行计划的方法有哪些问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"oracle查询执行计划的方法有哪些"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
1.explain plan for
--无需执行，快捷方便
--没有统计信息，产生的逻辑读，递归等
--无法判断处理了多少行
--无法判断表被访问了多少次
explain plan for select * from t,t1 where t.type=t1.object_name;
select * from table(dbms_xplan.display());
Plan hash value: 2914261090
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 221 | 244 (0)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 221 | 244 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL| T | 1 | 142 | 122 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| T1 | 1 | 79 | 122 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T"."TYPE"="T1"."OBJECT_NAME")
Note
-----
- dynamic statistics used: dynamic sampling (level=2)
19 rows selected.
2.set autotrace on
--有输出统计信息
--必须要等语句执行完之后才有结果--无法看到表被访问了多少次
set autotrace on ---set autotrace traceonly 不输出结果--
select * from t,t1 where t.type=t1.object_name;
Execution Plan
----------------------------------------------------------
Plan hash value: 2914261090
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 221 | 244 (0)| 00:00:01 |
|* 1 | HASH JOIN | | 1 | 221 | 244 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL| T | 1 | 142 | 122 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| T1 | 1 | 79 | 122 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T"."TYPE"="T1"."OBJECT_NAME")
Note
-----
- dynamic statistics used: dynamic sampling (level=2)
Statistics
----------------------------------------------------------
4 recursive calls
0 db block gets
896 consistent gets
0 physical reads
0 redo size
889 bytes sent via SQL*Net to client
408 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
3 rows processed
3.statistics_level=all
--可以从Starts看出表被访问多少次，E-Rows，A-Rows预测行数与真实行数，buffer是真实的逻辑读
---语句执行完后才有结果，无法控制不出结果，看不出递归调用和逻辑读
alter session set statistics_level=all;
select * from t,t1 where t.type=t1.object_name;
select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));
----------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
----------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | 896 | | | |
|* 1 | HASH JOIN | | 1 | 1 | 3 |00:00:00.01 | 896 | 1695K| 1695K| 787K (0)|
| 2 | TABLE ACCESS FULL| T | 1 | 1 | 4 |00:00:00.01 | 447 | | | |
| 3 | TABLE ACCESS FULL| T1 | 1 | 1 | 5 |00:00:00.01 | 449 | | | |
----------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T"."TYPE"="T1"."OBJECT_NAME")
Note
-----
- dynamic statistics used: dynamic sampling (level=2)
4.dbms_xplan.display_cursor
--知道sql_id可以立即得出真是的执行计划，且可以直接得出
--没有相关的统计信息（逻辑读等）--无法判断执行了多少次--无法得出表被访问了多少次
5qn0b7zft4s04
select * from table(dbms_xplan.display_cursor('sql_id'))--共享池获取
select * from table(dbms_xplan.display_awr('sql_id'))--awr性能视图中获取
select * from table(dbms_xplan.display_cursor('5qn0b7zft4s04'))
select * from table(dbms_xplan.display_awr('5qn0b7zft4s04'))
Plan hash value: 2914261090
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 244 (100)| |
|* 1 | HASH JOIN | | 1 | 221 | 244 (0)| 00:00:01 |
| 2 | TABLE ACCESS FULL| T | 1 | 142 | 122 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| T1 | 1 | 79 | 122 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("T"."TYPE"="T1"."OBJECT_NAME")
Note
-----
- dynamic statistics used: dynamic sampling (level=2)
5.10046 trace跟踪
--可以看出语句的等待事件，可以看出sql中的函数调用，
--可以看出处理的行数以及物理读--解析时间以及执行时间
--方便跟踪整个程序包
alter session set events '10046 trace name context forever,level 12'; 开启跟踪
执行语句
alter session set events '10046 trace name context off';
找到文件
tkprof trc文件 目标文件 sys=no sort=prsela,exeela,fchela
[oracle@oracle1 ~]$ cat 1.txt
TKPROF: Release 19.0.0.0.0 - Development on Wed Mar 11 10:25:48 2020
Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.
Trace file: NGENPR_ora_6661.trc
Sort options: prsela exeela fchela
********************************************************************************
count = number of times OCI procedure was executed
cpu = cpu time in seconds executing
elapsed = elapsed time in seconds executing
disk = number of physical reads of buffers from disk
query = number of buffers gotten for consistent read
current = number of buffers gotten in current mode (usually for update)
rows = number of rows processed by the fetch or execute call
********************************************************************************
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 2 0.00 0.00 0 138 0 0
Execute 2 0.00 0.00 0 0 0 0
Fetch 2 0.00 0.00 0 760 0 3
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 6 0.00 0.00 0 898 0 3
Misses in library cache during parse: 1
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
Disk file operations I/O 2 0.00 0.00
SQL*Net message to client 3 0.00 0.00
SQL*Net message from client 3 8.24 13.24
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 3 0.00 0.00 0 0 0 0
Execute 3 0.00 0.00 0 0 0 0
Fetch 3 0.00 0.00 0 136 0 2
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 9 0.00 0.00 0 136 0 2
Misses in library cache during parse: 3
Misses in library cache during execute: 1
2 user SQL statements in session.
3 internal SQL statements in session.
5 SQL statements in session.
********************************************************************************
Trace file: NGENPR_ora_6661.trc
Trace file compatibility: 12.2.0.0
Sort options: prsela exeela fchela
1 session in tracefile.
2 user SQL statements in trace file.
3 internal SQL statements in trace file.
5 SQL statements in trace file.
5 unique SQL statements in trace file.
167 lines in trace file.
5 elapsed seconds in trace file.
6 awrsqlrpt
@?/rdbms/admin/awrsqlrpt
begin end snap
sql_id
六种方法的差异
1.如果结果出不来，只能用1
2.比较简单的方法是1或者2
3.观察多个执行计划只能用4和6
4.如果语句复杂，里面涉及到函数等，只能用5
5.真实的执行计划不能用1
6.想获取表被访问的次数，只能用3
到此，关于"oracle查询执行计划的方法有哪些"的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注网站，小编会继续努力为大家带来更多实用的文章！
