我们看到,通过这两个Hints的联合使用,该查询首先对T_MAX和T_MIDDLE表进行HASH JOIN,再以这个结果集同T_SMALL进行HASH JION. 单纯通过Ordered和USE_HASH提示通常是达不到这个效果的: SQL> SELECT /*+ ordered use_hash(t_max t_middle) */ COUNT (*) 2 FROM t_max, t_middle,t_small 3 WHERE t_small...
我们看到,通过这两个Hints的联合使用,该查询首先对T_MAX和T_MIDDLE表进行HASH JOIN,再以这个结果集同T_SMALL进行HASH JION. 单纯通过Ordered和USE_HASH提示通常是达不到这个效果的: 这是Leading Hints在Oracle9i中的一个特殊用法.
我们看到,通过这两个Hints的联合使用,该查询首先对T_MAX和T_MIDDLE表进行HASH JOIN,再以这个结果集同T_SMALL进行HASH JION. 单纯通过Ordered和USE_HASH提示通常是达不到这个效果的: SQL> SELECT /*+ ordered use_hash(t_max t_middle) */ COUNT (*) 2 FROM t_max, t_middle,t_small 3 WHERE t_small...
看后面的hint use_hash(t2) 代表连接t2的方式是hash_join;然后用use_hash(t3)表示连接t3的方式是hash-join,那么谁作build表呢?看后面的swap_join_inputs(t3)代表t3作build表和t1-t2的结果集作连接...依此类推~ 标准的hint就应该这么写~ use_hash(x,y,z)这样的写法是不规范,这样只是说出了x,y,z地联...
使用leading和use_nl可以设置表的查询顺序,来加快查询速度, 比如有a,b,c,d四张表,a表的数据最少,如下设置 select /*+ leading(a) use_nl(a,b,c,d) index(a.id)*/ a.id from A 一般会将小表列为第一位 使用index直接匹配索引来查询数据提交查询速度...
Oracle Hint:USE_NL、USE_MERGE、UESE_HASH 2008-09-10 23:01 −下面内容取自http://yangtingkun.itpub.net/post/468/26696 一、USE_NL(嵌套循环连接) 在嵌套循环连接中,Oracle从第一个行源中读取第一行,然后和第二个行源中的数据进行对比。所有匹配的记录放在结果集中,然后Or... ...
1. 不使用任何hint,此时t2与t3表通过hash join进行连接。 select count(*) from t3,t2 where t2.object_id=t3.object_id; --- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --- | 0 |
Oracle Hint:USE_NL、USE_MERGE、UESE_HASH 2008-09-10 23:01 −下面内容取自http://yangtingkun.itpub.net/post/468/26696 一、USE_NL(嵌套循环连接) 在嵌套循环连接中,Oracle从第一个行源中读取第一行,然后和第二个行源中的数据进行对比。所有匹配的记录放在结果集中,然后Or... ...
During the summer of last year, there was a growing controversy surrounding the FDA’s request to hackers to expose holes in medical devices security, such as insulin devices and other wireless and computer connected home and hospital devices. Understandably, many hackers and security experts were ...
This post isn’t going to delve into all the different types of notes you can use. That would take up way too much space and frankly, there’s not enough time in the day to do that. Instead, my aim here is to give you an idea of how to make good use of your private notes, ...