[多项选择]Which two statements are true about the RMAN validate database command?（）
A. It checks the database for intrablock corruptions.
B. It can detect corrupt pfiles.
C. It can detect corrupt spfiles.
D. It checks the database for interblock corruptions.
E. It can detect corrupt block change tracking files.

[多项选择]Which two statements about sequences are true?（）
A. You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value.
B. You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence.
C. You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence.
D. You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column.
E. If a sequence starting from a value 100 and incremented by 1 is used by more then one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence.
F. You use REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.

[多项选择]Which two statements about subqueries are true?（）
A. A single row subquery can retrieve data from only one table.
B. A SQL query statement cannot display data from table B that is referred to in its subquery, unless table B is included in the main query's FROM clause.
C. A SQL query statement can display data from table B that is referred to in its subquery, without including table B in its own FROM clause.
D. A single row subquery can retrieve data from more than one table.
E. A single row subquery cannot be used in a condition where the LIKE operator is used for comparison.
F. A multiple-row subquery cannot be used in a condition where the LIKE operator is used for comparison.

[多项选择]Which two statements about views are true? （）
A. A view can be created as read only.
B. A view can be created as a join on two or more tables.
C. A view cannot have an ORDER BY clause in the SELECT statement.
D. A view cannot be created with a GROUP BY clause in the SELECT statement.
E. A view must have aliases defined for the column names in the SELECT statement.

[多项选择]Which three statements about subqueries are true? （）
A. A main query can have more than one subquery.
B. A subquery can have more than one main query.
C. The subquery and main query must retrieve data from the same table.
D. The subquery and main query can retrieve data from different tables.
E. Only one column or expression can be compared between the subquery and main query.
F. Multiple columns or expression can be compared between the subquery and main query.