choose threeorm
Which three statements are true about indexes and their administration in an Orade database?索引
A) An INVISIBLE index is not maintained when Data Manipulation Language (DML) is performed on its underlying table.three
B) An index can be created as part of a CREATE TABLE statement.ip
C) A DROP INDEX statement always prevents updates to the table during the drop opeatonci
D) A UNIQUE and non-unique index can be ceated on the same table colunnit
E) A descending index is a type of funcion-based indexio
F) If a query filters on an indexed column then it will always be used during execution of the queryevent
Answer：BCEtable
(解析：建表的時候就能夠建立索引;作 drop index 時會鎖表;form
建立降序排列的索引：
create index idx_emp_ename on emp(ename DESC) ;
建立了索引，在查詢的時候不必定都會用到，涉及的因素不少。
)