OCP 1Z0 051 48

48. Which two statements are true regarding indexes? (Choose two.) 
A. They can be created on tables and clusters. 
B. They can be created on tables and simple views. 
C. You can create only one index by using the same columns. 
D. You  can  create more  than  one  index  by  using  the  same  columns  if  you  specify  distinctly  different combinations of the columns. 

oracle没有视图索引 b不对

SQL> create or replace view v as select * from emp;View createdExecuted in 0.032 secondsSQL> create index idx_v on v(empno);create index idx_v on v(empno)ORA-01702: 视图不适用于此处

组合列，每种组合都可以建一个索引,c不对，d对.

SQL> create index idx_emp1 on emp(ename,job);Index createdSQL> create index idx_emp2 on emp(job,ename);Index created

Answer: AD