Example: All the alkanes have similar structures with single covalent bonds and show similar chemical properties, so they can be grouped together in the form of a homologous series.(b) (i) Esterification: An...
Query 和Current 的总和为所访问的逻辑缓冲区的总数 执行下面命令:tkprof D:\ORACLE\PRODUCT\10.2.0\DB_1\RDBMS\TRACE/wgods_ora_3940.trc h:\out.txtoutputfile explain=etl/etl 执行上面命令后,可以查看生成的文本文件 复制代码 代码如下: TKPROF: Release 10.2.0.1.0 - Production on 星期三 5月 23 16:...
General application incompatibility—This reason is a somewhat of a catch-all. For example, Azure SQL Database doesn't support cross-database querying, while managed instance does. Some applications require other services to coexist with the database instance in a manner that is...
Oracle 执行计划(Explain Plan) 说明 如果要分析某条SQL的性能问题,通常我们要先看SQL的执行计划,看看SQL的每一步执行是否存在问题。如果一条SQL平时执行的好好的,却有一天突然性能很差,如果排除了系统资源和阻塞的原因,那么基本可以断定是执行计划出了问题。 看懂执行计划也就成了SQL优化的先决条件。这里的SQL优化...
Scenarios differ from test cases in that test cases are written with single steps while scenarios generally cover numerous steps. The following is an example of a scenario that tests the interaction between a bank's customer support system and its ATM system. I am a customer of your bank. ...
SQL> @$ORACLE_HOME/rdbms/admin/utlxpls.sql Plan Table --- | Operation | Name | Rows | Bytes| Cost | Pstart| Pstop | --- | SELECT STATEMENT | | | | | | | | NESTED LOOPS | | | | | | |
However, these databases are not as popular as the traditional RDBMS. Some other areas of applications include office automation systems, decision support systems, Artificial Intelligence (AI) and expert systems, Neural networks and parallel programming, and Computer-Aided Design (CAD) systems. You’...
Action: Connect to the database as a user with SYSDBA privileges. Execute the ORACLE_HOME/rdbms/admin/initqsma.sql script. QSM-01001 query rewrite not enabled Cause: When query rewrite is disabled, no query rewrite will take place. Action: Enable query rewrite with ALTER SESSION SET QUERY_...
Why do we need an associative table for many-to-many relationships? The UNIQUE constraint differs from the PRIMARY KEY constraint in what way? What is the purpose of a database, and how does the database accomplish this purpose? What is a RDBMS ...
Example 9-2 Creating a PLAN_TABLE CONNECT HR/your_password@$ORACLE_HOME/RDBMS/ADMIN/UTLXPLAN.SQLTable created. Oracle Corporation recommends that you drop and rebuild thePLAN_TABLEtable after upgrading the version of the database because the columns might change. This can cause scripts to fail ...