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.
相关考题
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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
