Oracle檢視SQL執行計劃的方式
擷取Oracle sql執行計劃并檢視執行計劃，是掌握和判斷資料庫性能的基本技巧。下面案例介紹了多種檢視sql執行計劃的方式：
基本有以下幾種方式：
1、通過sql_trace初始化參數
2、通過Autotrace
3、通過explain plan
4、通過dbms_xplan.display_cursor
5、通過dbms_xplan.display_awr
6、通過10046事件
1、通過explain plan 工具
12:24:00 SCOTT@ prod>explain plan for
12:24:06 2 select empno,ename,sal,deptno from emp where empno=7788;
Explained.
Elapsed: 00:00:00.22
12:24:16 SCOTT@ prod>select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------
Plan hash value: 2949544139
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1 | 46 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 46 | 2 (0)| 00:00:01 |
|* 2 | INDEX UNIQUE SCAN | PK_EMP | 1 | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("EMPNO"=7788)
14 rows selected.
Elapsed: 00:00:01.14
2、通過DBMS_XPLAN.display_cursor檢視
12:52:37 SCOTT@ prod>desc dbms_xplan
FUNCTION DISPLAY_CURSOR RETURNS DBMS_XPLAN_TYPE_TABLE
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
SQL_ID VARCHAR2 IN DEFAULT
CURSOR_CHILD_NO NUMBER(38) IN DEFAULT
FORMAT VARCHAR2 IN DEFAULT
如果以scott使用者通路需要進行授權：
12:31:44 SYS@ prod>select * from dict where upper(table_name)=‘V$SESSION‘;
TABLE_NAME COMMENTS
------------------------------ ----------------------------------------
V$SESSION Synonym for V_$SESSION
Elapsed: 00:00:00.09
12:31:09 SYS@ prod>grant select on V_$SESSION to scott;
Grant succeeded.
Elapsed: 00:00:00.10
12:43:15 SCOTT@ prod>select * from table(dbms_xplan.display_cursor(null,null,‘advanced‘));
User has no SELECT privilege on V$SQL_PLAN
解決權限不足：
12:42:33 SYS@ prod>grant select any table to scott;
12:43:46 SYS@ prod>show parameter o7
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
O7_DICTIONARY_ACCESSIBILITY boolean TRUE
12:44:54 SYS@ prod>
案例：dbms_xplan.display_cursor
12:42:45 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
EMPNO ENAME SAL DEPTNO
---------- ---------- ---------- ----------
7788 SCOTT 3000 20
Elapsed: 00:00:00.08
12:43:15 SCOTT@ prod>select * from table(dbms_xplan.display_cursor(null,null,‘all‘));
SQL_ID bqz9ujgnn4jzu, child number 0
-------------------------------------
select empno,ename,sal,deptno from emp where empno=7788
| 0 | SELECT STATEMENT | | | | 2 (100)| |
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1 / EMP@SEL$1
2 - SEL$1 / EMP@SEL$1
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10], "SAL"[NUMBER,22],
"DEPTNO"[NUMBER,22]
2 - "EMP".ROWID[ROWID,10], "EMPNO"[NUMBER,22]
32 rows selected.
Elapsed: 00:00:00.05
案例：
12:49:10 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
Elapsed: 00:00:00.00
12:50:06 SCOTT@ prod>select * from table(dbms_xplan.display_cursor(null,null,‘advanced‘));
Outline Data
-------------
/*+
BEGIN_OUTLINE_DATA
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE(‘11.2.0.1‘)
DB_VERSION(‘11.2.0.1‘)
ALL_ROWS
OUTLINE_LEAF(@"SEL$1")
INDEX_RS_ASC(@"SEL$1" "EMP"@"SEL$1" ("EMP"."EMPNO"))
END_OUTLINE_DATA
*/
46 rows selected.
Elapsed: 00:00:00.06
12:50:21 SCOTT@ prod>
這種方法在 SQLPLUS中檢視剛執行過的 SQLSQLSQL的執行計劃 。
-- dbms_xplan.display_cursor傳入的前兩個參數值均為 null,null第三個參數是 "advanced"第三個參 數也可以是 "all"得到的顯示結果，少了 "Outline data"部分的内容 。
sql>select sql_text,sql_id,hash_value,child_number from v$sql
2* where sql_text like ‘select empno,ename,sal%‘
SQL_TEXT SQL_ID HASH_VALUE CHILD_NUMBER
-------------------------------------------------- ------------- ---------- ------------
select empno,ename,sal,deptno from emp where empno bqz9ujgnn4jzu 3913435130 0
=7788
Elapsed: 00:00:00.04
13:00:25 SCOTT@ prod>select * from table(dbms_xplan.display_cursor(‘bqz9ujgnn4jzu‘,0,‘advanced‘));
Elapsed: 00:00:00.14
3、通過DBMS_XPLAN.display_awr
使用方法dbms_xplan.display_cursor 能夠得到sql執行計劃的前提條件是該SQL還在共享池中，而如果執行計劃的前提條件是該SQL還在共享池中，而如果執行計劃的前提條件是該 還在共享池中，而如果SQLSQLSQL的執行計劃已經被刷出共享池，那麼隻要該SQL的執行計劃被ORACLE采集到 AWR Repository中， 就可以用該方法來檢視 。
12:24:00 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
13:10:56 SYS@ prod>exec dbms_workload_repository.create_snapshot;
PL/SQL procedure successfully completed.
13:11:37 SYS@ prod>alter system flush shared_pool;
System altered.
Elapsed: 00:00:00.31
13:16:28 SYS@ prod>select * from table(dbms_xplan.display_cursor(‘bqz9ujgnn4jzu‘,0,‘advanced‘));
SQL_ID: bqz9ujgnn4jzu, child number: 0 cannot be found
13:21:53 SYS@ prod>desc dbms_xplan
FUNCTION DISPLAY_AWR RETURNS DBMS_XPLAN_TYPE_TABLE
SQL_ID VARCHAR2 IN
PLAN_HASH_VALUE NUMBER(38) IN DEFAULT
DB_ID NUMBER(38) IN DEFAULT
13:30:15 SCOTT@ prod>select * from table(dbms_xplan.display_awr(‘bqz9ujgnn4jzu‘));
SQL_ID bqz9ujgnn4jzu
--------------------
| 2 | INDEX UNIQUE SCAN | PK_EMP | 1 | | 1 (0)| 00:00:01 |
Elapsed: 00:00:00.30
4、通過10046 事件檢視
1）檢視目前session：
13:29:52 SYS@ prod>grant alter session to scott;
13:44:31 SCOTT@ prod>alter session set events ‘10046 trace name context forever,level 12‘;
Session altered.
13:44:53 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
13:45:51 SCOTT@ prod>alter session set events ‘10046 trace name context off‘;
Elapsed: 00:00:00.03
[oracle@rh6 ~]$ ls -lt /u01/app/oracle/diag/rdbms/prod/prod/trace/|more
total 1256
-rw-r----- 1 oracle oinstall 27801 May 16 13:46 prod_ora_4995.trc
-rw-r----- 1 oracle oinstall 177 May 16 13:46 prod_ora_4995.trm
-rw-r----- 1 oracle oinstall 1122 May 16 13:34 prod_j000_5188.trc
-rw-r----- 1 oracle oinstall 59 May 16 13:34 prod_j000_5188.trm
......
[oracle@rh6 ~]$ tkprof /u01/app/oracle/diag/rdbms/prod/prod/trace/prod_ora_4995.trc /home/oracle/emp_0416.txt sys=no
TKPROF: Release 11.2.0.1.0 - Development on Fri May 16 13:47:41 2014
Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.
[oracle@rh6 ~]$ cat emp_0416.txt
SQL ID: bqz9ujgnn4jzu
Plan Hash: 2949544139
select empno,ename,sal,deptno
from
emp where empno=7788
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.07 0.09 1 66 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 0.00 0.00 0 2 0 1
total 4 0.07 0.09 1 68 0 1
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 84
Rows Row Source Operation
------- ---------------------------------------------------
1 TABLE ACCESS BY INDEX ROWID EMP (cr=2 pr=0 pw=0 time=0 us cost=2 size=46 card=1)
1 INDEX UNIQUE SCAN PK_EMP (cr=1 pr=0 pw=0 time=0 us cost=1 size=0 card=1)(object id 73202)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file sequential read 1 0.00 0.00
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 19.13 19.13
********************************************************************************
2）檢視其它session：
14:12:23 SYS@ prod>select sid,serial#,username from v$session where username is not null;
SID SERIAL# USERNAME
---------- ---------- ------------------------------
1 5 SYS
42 9 SCOTT
6 rows selected.
14:12:47 SYS@ prod>desc dbms_monitor
PROCEDURE SESSION_TRACE_DISABLE
SESSION_ID BINARY_INTEGER IN DEFAULT
SERIAL_NUM BINARY_INTEGER IN DEFAULT
PROCEDURE SESSION_TRACE_ENABLE
WAITS BOOLEAN IN DEFAULT
BINDS BOOLEAN IN DEFAULT
PLAN_STAT VARCHAR2 IN DEFAULT
14:13:11 SCOTT@ prod>select sid from v$mystat where rownum=1;
SID
----------
42
14:13:41 SYS@ prod>exec dbms_monitor.SESSION_TRACE_ENABLE(42,9,waits=>true,binds=>true);
14:13:25 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7369;
7369 SMITH 800 20
14:14:29 SYS@ prod>exec dbms_monitor.SESSION_TRACE_disable(42,9);
Elapsed: 00:00:00.02
SQL ID: fyydvbdw2uq6q
emp where empno=7369
Parse 1 0.00 0.00 0 0 0 0
total 4 0.00 0.00 0 2 0 1
SQL*Net message from client 1 0.00 0.00
5、通過autotrace檢視
SET AUTOTRACE ON
SET AUTOTRACE TRACEONLY
SET AUTOTRACE TRACEONLY EXPLAIN
--使用SET AUTOTRACE ON和SET AUTOTRACE TRACEONLY時，目标SQL已經被執行過，是以在SET AUTOTRACE ON和SET AUTOTRACE TRACEONLY 的情況下能看到目标SQL
的實際消耗情況。
--使用SET AUTOTRACE TRACEONLY EXPLAIN時，如果執行的是SELECT語句，則該SQL并沒有被執行，但如果執行的是DML語句，情況就不一樣了，此時的DML語句是會
被ORACLE執行的。
--需要特别說明的是，雖然使用SET AUTOTRACE指令所得到的執行計劃可能是不準确的，因為SET AUTOTRACE指令所顯示的執行計劃都是源自于explain plan 指令。
15:32:11 SYS@ prod>conn scott/tiger
Connected.
15:32:17 SCOTT@ prod>set autotrace on
15:32:21 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
Execution Plan
----------------------------------------------------------
Statistics
168 recursive calls
0 db block gets
38 consistent gets
0 physical reads
0 redo size
736 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
5 sorts (memory)
0 sorts (disk)
1 rows processed
15:32:26 SCOTT@ prod>set autotrace trace
15:32:49 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
0 recursive calls
2 consistent gets
0 sorts (memory)
15:34:59 SCOTT@ prod>set autotrace on exp
15:35:04 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
15:35:12 SCOTT@ prod>set autotrace on statis
15:35:20 SCOTT@ prod>select empno,ename,sal,deptno from emp where empno=7788;
15:35:26 SCOTT@ prod>
@至此，Oracle下檢視SQL執行計劃的幾種方式介紹完畢，大家可根據自己的愛好來使用！
本文出自 “” 部落格，請務必保留此出處
![oracle中的start with connect by用法[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)