1.explain plan的使用
SQL> explain plan for delete from t_jingyu; Explained. SQL> select * from table(dbms_xplan.display); PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1368587462 -----------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
-----------------------------------------------------------------------
| 0 | DELETE STATEMENT | | 1864K| 978 (2)| 00:00:12 |
| 1 | DELETE | T_JINGYU | | | |
| 2 | TABLE ACCESS FULL| T_JINGYU | 1864K| 978 (2)| 00:00:12 |
----------------------------------------------------------------------- Note
-----
- dynamic sampling used for this statement (level=2) 13 rows selected
2.explain plan 只是显示执行计划，并不会真正执行delete语句·
SQL> select count(*) from t_jingyu; COUNT(*)
----------
2097152