单项选择题 What is the correct order of the following commands if you wanted to restore datafile 4， which was accidentally removed from the file system？（）   a. sql ’alter database datafile 4 online’ b. restore datafile 4 c. recover datafile 4  d. sql ’alter database datafile 4 offline’ e. startup  f. shutdown

单项选择题 You have a very large table that your users access frequently. Which of the following advisors will recommend any indexes to improve the performance of queries against this table?（）

多项选择题 Which of the following cannot be used as input to the SQL Tuning Advisor?（） (Choose all that apply.)