多项选择题

Which two statements are true regarding B-tree index（）

A.The leaf blocks in the index are doubly linked.
B.The leaf node stores a bitmap for each key value.
C.The rows with NULL value in key columns also have entries in the index.
D.The deletion of a row from the table causes a logical deletion in index leaf block and the space becomes available for the new leaf entry.

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单项选择题Whichstatementdescribestheeffectonanindex，whentheindexedcolumnfortherowsisupdatedinthebasetable（）

A.An update in a leaf row takes place.
B.The index becomes invalid after the update.
C.The leaf block containing the row to be updated is marked as invalid.
D.A row in the leaf block of the index for the key value is logically deleted and a new leaf row is inserted

多项选择题The session of user SCOTT receives the following error after executing an UPDATE command onthe EMP table： ERROR at line 1： ORA-00060： deadlock detected while waiting for resource On investigation， you find that a session opened by user JIM has a transaction that caused the deadlock. two statements are true regarding the session of SCOTT in this scenario（）

A.The session is terminated after receiving the error and JIM can continue with his transaction.
B.SCOTT should perform a COMMIT or ROLLBACK to allow JIM to continue with his transaction.
C.The session is rolled back after receiving the error and JIM can continue with his transaction.
D.SCOTT has to reexecute the last command in the transaction after he commits the transaction.

单项选择题The table contains a million rows for zonewise analysis in the DSS system. DML operations areperformed very rarely on the table. You decide to prepare an index on the ZONE column to enhance theperformance of the queries on the ZONE column. Which type of index would you select in this scenario（）

A.Bitmap index
B.Reverse key index
C.Normal B-Tree index
D.Function-based index

单项选择题You have two tables with referential integrity enforced between them. You need to insert data to thechild table first because it is going to be a long transaction and data for the parent table will be available ina later stage， which can be inserted as part of the same transaction. View the Exhibit to examine the commands used to create tables. Which action would you take to delay the referential integrity checking until the end of the transaction（）

A.Set the constraint to deferred before starting the transaction.
B.Alter the constraint to NOVALIDATE state before starting the transaction.
C.Enable the resumable mode for the session before starting the transaction.
D.Set the COMMIT_WAIT parameter to FORCE_WAIT for the session before starting the transaction.

多项选择题You execute this command to drop the ITEM table， which has the primary key referred in the ORDERtable： SQL> DROP TABLE scott.item CASCADE CONSTRAINTS PURGE； Which two statements are true about the effect of the command（）

A.No flashback is possible to bring back the ITEM table.
B.The ORDER table is dropped along with the ITEM table.
C.The dependent referential integrity constraints in the ORDER table are disabled.
D.The dependent referential integrity constraints in the ORDER table are removed.
E.The table definition of the ITEM table and associated indexes are placed in the recycle bin.