单项选择题
All the database users are presently connected to the database instance and working. The HR userhas opened three database sessions and executed the following command in one of his sessions： SQL> UPDATE persons SET ccode=’U031’ WHERE ccode=’U029’； 123 rows updated.
SQL> DELETE FROM persons WHERE exp=’Y’； 3 rows deleted.
The SYS user opens a new session after HR executed the above commands.
Which sessions can seethe effect of the UPDATE and DELETE commands （）
A.all sessions of the HR user only
B.all sessions of the HR user and the SYS user
C.the session of the HR user that executed the commands
D.all the sessions for which the database users have access privilege to the PERSONS table
相关考题
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单项选择题
You executed this command to create a temporary table： SQL> CREATE GLOBAL TEMPORARY TABLE report_work_area （startdate DATE， enddate DATE， class CHAR（20））ON COMMIT PRESERVE ROWS； Which statement is true about the rows inserted into the REPORT_WORK_AREA table during atransaction （）
A.The rows stay in the table only until session termination.
B.The rows stay in the table only until the next transaction starts on the table.
C.The rows are visible to all current sessions after the transaction is committed.
D.The rows stay available for subsequent sessions after the transaction is committed -
多项选择题
WhichtwostatementsaretrueregardingB-treeindex（）
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. -
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
