理论上来说,嵌套循环连接等于两个嵌套的循环,比如说employees表和departments表之间的嵌套循环连接,可以看成是: FOR erow IN (select * from employees where X=Y) LOOP FOR drow IN (select * from departments where erow is matched) LOOP output values from erow and drow END LOOP END LOOP 可以看出,外...
Cursor for loop for rec in (select col_1, col_2 from table_a) loop /*Statements, use rec.col_1 and rec.col_2 */ end loop; for rec in cursor_name loop /*Statements, use rec.col_1 and rec.col_2 */ end loop; for rec in cursor_name(cursor_param_1, cursor_param_2...) lo...
用sys用户运行脚本ultxplan.sql 建立这个表的脚本是:rdbms\admin)ultxplan.sql。 SQL> connect sys/sys@colm2 as sysdba; SQL> @rdbms\admin\utlxplan.sql; SQL> create public synonym plan_table for plan_table;--建立同义词 SQL> grant all on plan_table to public;--授权所有用户 要在数据库中建立...
Cursor for loop for rec in (select col_1, col_2 from table_a) loop /*Statements, use rec.col_1 and rec.col_2 */ end loop; for rec in cursor_name loop /*Statements, use rec.col_1 and rec.col_2 */ end loop; for rec in cursor_name(cursor_param_1, cursor_param_2...) lo...
表T1和T2在施加了目标SQL中指定的谓词条件(如果有的话)后得到的结果集中数据量较小的那个结果集(S)会被Oracle选为哈希连接的驱动结果集,T2所对应的结果集的数据量相对较大,我们记为B;S是驱动结果集,B是被驱动结果集;接着Oracle会遍历S,读取S中的每一条记录,并对S中的每一条记录按照该记录在表T1中的连接...
Name CTL-08: Scan collections using FIRST, LAST, and NEXT in loops. Synopsis A collection in PL/SQL is like a single-dimensional array. A collection differs from an array, however, in that … - Selection from Oracle PL/SQL Best Practices [Book]
This is the quickest access method available.Oracle retrieves the specified block and extracts the rows it is interested in. --Rowid扫描是最快的访问数据方式 七、运算符 1.sort --排序,很消耗资源 There are a number of different operations that promote sorts: ...
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO courts.20100625 (idtime, time, court) VALUES ('6002', ' at line 2) Any idea what I'm doing wrong here?Navigate...
首先，每隔一段时间要对经常用到的表进行统计分析（analyze table），让oracle分析出最合适的执行计划； 如果要一直监控sql的执行计划，可以使用trace工具，这个是对session级运行的， exec dbms_system.set_sql_trace_in_session(SID,SERIAL#,t
Oracle数据库体系物理结构【直播】Oracle数据库体系结构概述(1月7日 09:30-17:30)06后台进程架构【直播】1.5一条SQL在Oracle数据库(1月8日 09:30-17:30)07Oracle 数据库逻辑结构【直播】表空间(1月9日 09:30-17:30)08体系架构实战【直播】体系架构实战(1月10日 09:30-17:30)09管理Oracle数据库实例【...