如果使用sqlplus，可以使用set autotrace命令来得到后续执行sql的执行计划。
语法如下：
SET AUTOT[RACE] {OFF|ON|TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]

SQL> set autotrace traceonly
--以上表示只生成执行计划，不将SQL结果显示出来。
SQL> select employee_id,last_name,salary from employees where employee_id=100;

Execution Plan
----------------------------------------------------------
Plan hash value: 1833546154

---------------------------------------------------------------------------------------------
| Id | Operation                   | Name          | Rows | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |               |     1 |    16 |     1   (0)| 00:00:01 |
|   1 | TABLE ACCESS BY INDEX ROWID| EMPLOYEES     |     1 |    16 |     1   (0)| 00:00:01 |
|* 2 |   INDEX UNIQUE SCAN         | EMP_EMP_ID_PK |     1 |       |     0   (0)| 00:00:01 |
---------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

2 - access("EMPLOYEE_ID"=100)

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

可以看到使用这种方式还可以得到sql执行所耗费的物理读、逻辑读等统计信息。

Oracle查看执行计划（二）