使用autotrace查看执行计划
set autotrace off
不产生autotrace报告，默认值set autotrace on explain
autotrace报告只展示最优的执行方式（optimizer execution path）SQL> set autotrace on explain;
—插入数据测试是否执行了sql
SQL> insert into scott.emp values('5566','explain','','','','','','');
1 row created.
—已经表明执行了sql
—只展示了执行计划
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报告sql执行统计信息（SQL statement execution statistics. ）SQL> set autotrace on statistics;
SQL> insert into scott.emp values('6677','statistics','','','','','','');
1 row created.
—说明执行了sql
—只展示sql执行的统计信息
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报告包含了最优执行方式和sql执行统计信息SQL> set autotrace on;
SQL> insert into scott.emp values('8899','on','','','','','','');
1 row created.
—相当于set autotrace on explain和set autotrace on statistics的和，既输出执行计划，也输出统计信息，同时也执行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类似，但是不输出用户查询的结果SQL> set autotrace traceonly;
SQL> insert into scott.emp values('9900','traceonly','','','','','','');
1 row created.
—与set autotrace on 类似，都会输出执行计划和统计信息
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;
—与set autotrace on不同的是，没有输出查询结果
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>
网页题目：使用autotrace查看执行计划
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