多項選擇題

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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單項選擇題

Which statement describes the effect on an index， when the indexed column for the rows is updatedin the base table（）

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

多項選擇題

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.