Oracle执行计划之入门（1）

第一种执行计划：

SQL> explain plan
  2 set statement_id ='test1'
  3 into plan_table
  4 for select * from daiqi.t_baidu_doc
  5 ;

Explained.

SQL> select lpad(' ',level-1)||operation||' '||options||' '||
  2  object_name "PLan"
  3 from plan_table
  4 connect by prior id= parent_id
  5 and prior statement_id = statement_id
  6 start with id =0 and statement_id ='&1'
  7 order by id;
Enter value for 1: test1
old   6: start with id =0 and statement_id ='&1'
new   6: start with id =0 and statement_id ='test1'

PLan
--------------------------------------------------------------------------------
SELECT STATEMENT
 TABLE ACCESS FULL T_BAIDU_DOC

第二种执行计划：

SQL> explain plan for
  2 select * from daiqi.t_baidu_doc;

Explained.

SQL> set linesize 130;
SQL> set pagesize 0;
SQL> select * from table(DBMS_XPLAN.DISPLAY);
Plan hash value: 149575921

---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 4848K| 795M| 31955 (1)| 00:06:24 |
| 1 | TABLE ACCESS FULL| T_BAIDU_DOC | 4848K| 795M| 31955 (1)| 00:06:24 |

第三种执行计划:

SQL>@$ORACLE_HOME/rdbms/admin/utlxplan.sql

Autotrace特性.

SET AUTOTRACE ON EXPLAIN: 此选项仅生成执行计划，不执行查询本身.
SET AUTOTRACE ON STATISTICS: 此选项仅显示SQL语句的执行统计数据.
SET AUTOTRACE ON: 此选项既显示执行计划,又显示SQL语句的执行统计数据

SQL> set autotrace on explain;
SQL> select count(*) from daiqi.t_baidu_doc;

  COUNT(*)
----------
   4848509


Execution Plan
----------------------------------------------------------
Plan hash value: 4162034560

------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 2858 (2)| 00:00:35 |
| 1 | SORT AGGREGATE | | 1 | | |
| 2 | INDEX FAST FULL SCAN| SYS_C0010938 | 4848K| 2858 (2)| 00:00:35 |
------------------------------------------------------------------------------

SQL>