1.While deploying a new application module,the software vendor ships the application software along with appropriate SQL plan baselines for the new SQLs being introduced.Which two statements describe the consequences?(Choose two.) A.The plan baselin
oracle一些基本的SQL优化,适合入门讲座
ORACLE的优化器共有3种:
a. RULE (基于规则rbo) b. COST (基于成本cbo)
c. CHOOSE (选择性)
设置缺省的优化器,可以通过对init.ora文件中 OPTIMIZER_MODE参数的各种声明,如RULE,COST,CHOOSE,ALL_ROWS,FIRST_ROWS . 你当然也可在SQL句级或是会话(session)级对其进行覆盖