SQL> explain plan for select /*+ use_nl(t1,t2) */ t1.owner,t1.object_name,t2.status from t1,t2 where t1.id=t2.id and t2.status='VALID'; Explained SQL> select OPERATION,OPTIONS,IO_COST,CPU_COST FROM PLAN_TABLE; OPERATION OPTIONS IO_COST CPU_COST --- --- --- --- SELECT ...
2.表之间的连接用了hash Join,Nested loops,Sort Merge Join 多表之间的连接有三种方式:Nested Loops,Hash Join和Sort Merge Join.下面来介绍三种不同连接的不同: 一.NESTED LOOP: 对于被连接的数据子集较小的情况,嵌套循环连接是个较好的选择。在嵌套循环中,内表被外表驱动,外表返回的每一行都要在内表中检索...
“Unable to enlist in the transaction” with Oracle linked server from MS SQL Server [<Name of Missing Index, sysname,>] in non clustered index [Execute SQL Task] Error: The value type (__ComObject) can only be converted to variables of type Object. [ODBC Driver Manager] Data source nam...
Implementing a join via nested loops on a columnar structure is actually rather inefficient. To draw a parallel here: imagine what work would be required on a DBMS like Oracle, if the nested loop join would have to use BITMAP indexes. So, what join algorithm does SAP HANA use now? For ...
Pushed into mysql-trunk 5.6.99-m5 (revid:alexander.nozdrin@oracle.com-20101113155825-czmva9kg4n31anmu) (version source revid:vasil.dimov@oracle.com-20100629074804-359l9m9gniauxr94) (merge vers: 5.6.99-m4) (pib:21) [23 Nov 2010 3:14] Paul DuBois ...
Oracle SQL 性能调优:使用Hint固定执行计划1(Hash Join) Nested Loop Join 指定时用到的 Hint 和Hash Join 相对应的,通常,利用索引时一般会用到 Nested Loop Join。 下面我们来继续看看如何控制 Nested Loop Join 的使用,以及 Nested Loop Join 的顺序。 LEADING Hint (指定 Nested Loop Join 顺序) USE_NL (...
@@FETCH_STATUS in nested loops @@ServerName returns wrong value in SQL SERVER 2008 ##TempTable and INSERT-SELECT FROM an existing Table with an IDENTITY column %rowtype equivalent in SQL server ++ operator in TSQL - bug or feature? 2 tables referencing each other using foreign key.is i...
“Unable to enlist in the transaction” with Oracle linked server from MS SQL Server [<Name of Missing Index, sysname,>] in non clustered index [Execute SQL Task] Error: The value type (__ComObject) can only be converted to variables of type Object. [ODBC Driver Manager] Data source nam...