日前oracle使用总结

最近oracle使用总结

1：查看sql的执行计划

explain plan for sql

然后执行select * from table(dbms_xplan.display());

例如

explain plan for select rownum no,id,name from product_group order by name

然后执行select * from table(dbms_xplan.display());

输出为

 
-----------------------------------
| Id  | Operation            |  Name          | Rows  | Bytes | Cost  |
-----------------------------------
|   0 | SELECT STATEMENT     |                |       |       |       |
|   1 |  SORT ORDER BY       |                |       |       |       |
|   2 |   COUNT              |                |       |       |       |
|   3 |    TABLE ACCESS FULL | PRODUCT_GROUP  |       |       |       |
-----------------------------------
 
Note: rule based optimization