使用autotrace查看執(zhí)行計劃

set autotrace off

不產(chǎn)生autotrace報告，默認值

set autotrace on explain

autotrace報告只展示最優(yōu)的執(zhí)行方式（optimizer execution path）
SQL> set autotrace on explain;
—插入數(shù)據(jù)測試是否執(zhí)行了sql
SQL> insert into scott.emp values('5566','explain','','','','','','');

1 row created.
—已經(jīng)表明執(zhí)行了sql
—只展示了執(zhí)行計劃
Execution Plan
----------------------------------------------------------
---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 1 | 100 | 1 (0)| ss00:00:01 |
| 1 | LOAD TABLE CONVENTIONAL | EMP | | | | |
---------------------------------------------------------------------------------

SQL> select * from scott.emp where empno=5566;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
5566 explain

Execution Plan
----------------------------------------------------------
Plan hash value: 2949544139
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 87 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 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"=5566)

set autotrace on statistics

autotrace報告sql執(zhí)行統(tǒng)計信息（SQL statement execution statistics. ）
SQL> set autotrace on statistics;
SQL> insert into scott.emp values('6677','statistics','','','','','','');

1 row created.
—說明執(zhí)行了sql
—只展示sql執(zhí)行的統(tǒng)計信息
Statistics
----------------------------------------------------------
52 recursive calls
5 db block gets
80 consistent gets
0 physical reads
520 redo size
839 bytes sent via SQL*Net to client
826 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
10 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> select * from scott.emp where empno=6677;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
6677 statistics

Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
2 consistent gets
0 physical reads
0 redo size
869 bytes sent via SQL*Net to client
512 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

set autotrace on

autotrace報告包含了最優(yōu)執(zhí)行方式和sql執(zhí)行統(tǒng)計信息
SQL> set autotrace on;
SQL> insert into scott.emp values('8899','on','','','','','','');

1 row created.

—相當于set autotrace on explain和set autotrace on statistics的和，既輸出執(zhí)行計劃，也輸出統(tǒng)計信息，同時也執(zhí)行sql
Execution Plan
----------------------------------------------------------

---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 1 | 100 | 1 (0)| 00:00:01 |
| 1 | LOAD TABLE CONVENTIONAL | EMP | | | | |
---------------------------------------------------------------------------------

Statistics
----------------------------------------------------------
45 recursive calls
5 db block gets
77 consistent gets
0 physical reads
512 redo size
839 bytes sent via SQL*Net to client
816 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
10 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> select * from scott.emp where empno=8899;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
8899 on

Execution Plan
----------------------------------------------------------
Plan hash value: 2949544139
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 87 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 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"=8899)
Statistics
----------------------------------------------------------
9 recursive calls
0 db block gets
18 consistent gets
0 physical reads
0 redo size
861 bytes sent via SQL*Net to client
512 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

set autotrace traceonly

和set autotrace on類似，但是不輸出用戶查詢的結(jié)果
SQL> set autotrace traceonly;
SQL> insert into scott.emp values('9900','traceonly','','','','','','');
1 row created.
—與set autotrace on 類似，都會輸出執(zhí)行計劃和統(tǒng)計信息
Execution Plan
----------------------------------------------------------
---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 1 | 100 | 1 (0)| 00:00:01 |
| 1 | LOAD TABLE CONVENTIONAL | EMP | | | | |
---------------------------------------------------------------------------------

Statistics
----------------------------------------------------------
108 recursive calls
5 db block gets
191 consistent gets
1 physical reads
520 redo size
839 bytes sent via SQL*Net to client
825 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
15 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> select * from scott.emp where empno=9900;
—與set autotrace on不同的是，沒有輸出查詢結(jié)果
Execution Plan
----------------------------------------------------------
Plan hash value: 2949544139
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 87 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 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"=9900)
Statistics
----------------------------------------------------------
9 recursive calls
0 db block gets
18 consistent gets
0 physical reads
0 redo size
867 bytes sent via SQL*Net to client
512 bytes received via SQL*Net from client
1 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

SQL>

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