Which object may be used during query optimization to improve the performance for a subset of SELECT queries?（）

单项选择题To which of the following resources can a lock be applied?（）

A.Row
B.Alias
C.Bitmap
D.Column

单项选择题Application A holds an Update lock on a single row and application B is trying to read that row. If both applications are using isolation level UR, which of the following will occur?（）

A.Application B will read the row.
B.Applications A and B will cause a deadlock situation.
C.Application B will wait until application A releases the Update lock.
D.Application A will be terminated so that application B can read the row.

单项选择题Application A is designed to execute the following SQL statements within a single Unit of Work (UOW). UPDATE employee SET salary = salary * 1.1 WHERE empno=000010 UPDATE department SET deptname = NEW dept WHERE deptno=A00Application B is designed to execute the following SQL statements within a single Unit of Work (UOW). UPDATE department SET deptname = OLD DEPT WHERE deptno=A00 UPDATE employee SET salary = salary * 0.5 WHERE empno=000010 Application A and application B execute their first SQL statement at the same time. When application A and application B try to execute their second SQL statement, a deadlock occurs. What will happen?（）

A.The database manager will rollback the transaction in both applications.
B.The database manager will rollback the transaction in one of the two applications.
C.Application B will successfully update the EMPLOYEE and DEPARTMENT tables; Application A will be placed in a lock wait state.
D.Application A will successfully update the EMPLOYEE and DEPARTMENT tables; Application B will terminate when the lock timeout value is reached.

单项选择题Which of the following is TRUE for the DB2 isolation level Cursor Stability (CS)?（）

A.An application process acquires at least a share lock on the current row of every cursor.
B.Any row that is read during a unit of work cannot be changed by other application processes until the unit of work is complete.
C.Any row changed by another application process can be read, even if the change has not been committed by that application process.
D.An application process that issues the same query more than once in a unit of work will not see additional rows caused by other application processes appending new information to the database.

单项选择题Which of the following best describes the lock protection provided by DB2 for the current row of a cursor?（）

A.The cursor is only protected from updates and deletes by concurrent applications.
B.The row is only protected from positioned updates and deletes that reference another cursor of the same application.
C.The cursor is protected from positioned updates and deletes that reference another cursor of a different application.
D.The row is protected from updates and deletes by the current application and from positioned updates and deletes that reference another cursor of the same application.