DBMS_XPLAN Package来查看执行计划

查看执行计划除了AUTOTRACE的方法外，还可以使用DBMS_XPLAN Package来查看

1.执行"explain Plan"
语法:
SQL> Explain plan for
Try this command:
SQL> explain plan for select * from mtl_system_items_b where inventory_item_id = 149 and organization_id = 207;
Explained
这个命令会产生执行计划，并把执行计划保存到"PLAN_TABLE"中。2.查看执行计划
SQL> select * from table(dbms_xplan.display);(dbms_xplan.display() is a packaged function used to view the execution plan generated.)
Output like:
SQL> select * from table(dbms_xplan.display); PLAN_TABLE_OUTPUT-------------------------------------------------------------------------------------------------------------Plan hash value: 780806759 -----------------------------------------------------------------------------------------------------| Id  | Operation                   | Name                  | Rows  | Bytes | Cost (%CPU)| Time     |-----------------------------------------------------------------------------------------------------|   0 | SELECT STATEMENT            |                       |     1 |   554 |     2   (0)| 00:00:01 ||   1 |  TABLE ACCESS BY INDEX ROWID| MTL_SYSTEM_ITEMS_B    |     1 |   554 |     2   (0)| 00:00:01 ||*  2 |   INDEX UNIQUE SCAN         | MTL_SYSTEM_ITEMS_B_U1 |     1 |       |     1   (0)| 00:00:01 |----------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id):---------------------------------------------------    2 - access("INVENTORY_ITEM_ID"=149 AND "ORGANIZATION_ID"=207) 已选择14行。
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原文链接：https://blog.csdn.net/pan_tian/article/details/8028417