[每日一题]OCP1z0-047 :2013-07-30表连接??内联视图当作表使用

[每日一题]OCP1z0-047 :2013-07-30表连接??内联视图当作表使用

[每日一题]OCP1z0-047 :2013-07-30表连接??内联视图当作表使用

[每日一题]OCP1z0-047 :2013-07-30表连接??内联视图当作表使用

用sys用户登录,给oe用户授权dba,以便可以用oe用户查看执行计划:

[email protected]> conn / as sysdba Connected. [email protected]> grant dba to oe; Grant succeeded. [email protected]> conn oe/oe Connected. [html] [email protected]> set autot traceonly; [email protected]> SELECT p.product_name,i.item_cnt 2 FROM (SELECT product_id,COUNT(*) item_cnt 3 FROM order_items 4 GROUP BY product_id) i RIGHT OUTER JOIN products p ON i.product_id=p.product_id; 288 rows selected. Execution Plan ---------------------------------------------------------- Plan hash value: 1905807913 ----------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 288 | 24768 | 97 (3)| 00:00:02 | |* 1 | HASH JOIN RIGHT OUTER | | 288 | 24768 | 97 (3)| 00:00:02 | | 2 | VIEW | index$_join$_006 | 288 | 11520 | 88 (2)| 00:00:02 | |* 3 | HASH JOIN | | | | | | |* 4 | INDEX FAST FULL SCAN| PRD_DESC_PK | 288 | 11520 | 41 (0)| 00:00:01 | | 5 | INDEX FAST FULL SCAN| PROD_NAME_IX | 288 | 11520 | 68 (0)| 00:00:01 | |* 6 | HASH JOIN RIGHT OUTER | | 288 | 13248 | 9 (12)| 00:00:01 | | 7 | VIEW | | 185 | 4810 | 3 (0)| 00:00:01 | | 8 | HASH GROUP BY | | 185 | 740 | 3 (0)| 00:00:01 | | 9 | INDEX FULL SCAN | ITEM_PRODUCT_IX | 665 | 2660 | 3 (0)| 00:00:01 | | 10 | TABLE ACCESS FULL | PRODUCT_INFORMATION | 288 | 5760 | 5 (0)| 00:00:01 | ----------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("D"."PRODUCT_ID"(+)="I"."PRODUCT_ID") 3 - access(ROWID=ROWID) 4 - filter("D"."LANGUAGE_ID"=SYS_CONTEXT('USERENV','LANG')) 6 - access("I"."PRODUCT_ID"(+)="I"."PRODUCT_ID") Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 135 consistent gets 0 physical reads 0 redo size 14913 bytes sent via SQL*Net to client 733 bytes received via SQL*Net from client 21 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 288 rows processed

可以看看执行计划,了解一下sql 执行的步骤。

答案A是正确的:查询出结果288 行,说明可以正常执行并返回结果

答案B是不正确的:我们可以把内联视图看成是一个独立的表,它是可以与其它表做外连接的。

答案C是不正确的:内联视图聚合函数的别名可以看作一个列名展显出来

答案D是不正确的:group by可以用在内联视图

正确答案是:A

这道题目太简单了,没什么好说的,写过SQL的人,直接可以PASS了。

分类:默认分类 时间:2015-03-13 人气:1
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