查看执行计划方法总结之一:explain plan命令

查看执行计划的方法有很多种，笔者今后将在博客里一一为大家介绍。本文介绍的是第一种方法，利用explain plan命令来查看执行计划

查看执行计划的方法有很多种，笔者今后将在博客里一一为大家介绍。本文介绍的是第一种方法，利用explain plan命令来查看执行计划。

1.用hr用户登录数据库
[Oracle@ENMOEDU ~]$ sqlplus hr/oracle@ENMOEDU

SQL*Plus: Release 11.2.0.3.0 Production on Thu Apr 10 00:11:00 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

HR@ENMOEDU >

2.使用explain plan命令
HR@ENMOEDU > explain plan for select salary from employees where first_name like 'Pat';

Explained.

3.查看执行计划
HR@ENMOEDU > select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
------------------------------------------------------------------------
Plan hash value: 3033625502
-------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 11 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMPLOYEES | 1 | 11 | 2 (0)| 00:00:01 |
|* 2 | INDEX SKIP SCAN | EMP_NAME_IX | 1 | | 1 (0)| 00:00:01 |
-------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("FIRST_NAME"='Pat')
filter("FIRST_NAME"='Pat')

15 rows selected.

至此，，执行计划查看成功。