单选题Given table T1 has column I1 containing the following data: I1 1 2 3 4 If the following sequence of SQL statements is applied within a single unit of work: UPDATE t1 SET i1 = 3 WHERE i1 = 2; S AVEPOINT s1 ON ROLLBACK RETAIN CURSORS; UPDATE t1 SET i1 =

第1题：

第2题：

第3题：

两电阻相并联，已知R₁/R₂=1/2，则流入电阻的电流之比I1/I2、功率之比P1/P2分别是（）。

• A、I1/I2=2，P1/P2=2
• B、I1/I2=2，P1/P2=4
• C、I1/I2=1/2，P1/P2=1/2
• D、I1/I2=2，P1/P2=1/4

第4题：

已知两个正弦量分别为i₁=-4cos（100t+60°）A，i₂=4cos（100t+30°）A，则i₁和i₂的相位差为（）。

• A、i₁超前i₂30°
• B、i₁滞后i₂30°
• C、i₁超前i₂150°
• D、i₁滞后i₂150°

第5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='A00'Application 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.

第6题：

Assuming PUBLIC has been granted all privileges on table T1, which of the following statements would continue to permit any user to add rows to table T1, but not remove them?（）

• A、REVOKE DROP ON t1 FROM PUBLIC
• B、REVOKE UPDATE ON t1 FROM PUBLIC
• C、REVOKE DELETE ON t1 FROM PUBLIC
• D、REVOKE CONTROL ON t1 FROM PUBLIC

第7题：

User SCOTT executes the following command on the EMP table but has not issued COMMIT， ROLLBACK， or any data definition language （DDL） command： SQL> SELECT ename FROM emp  2 WHERE job=’CLERK’ FOR UPDATE OF empno；  SCOTT has opened another session to work with the database instance.  Which three operations wouldwait when issued in SCOTT’s second session（）

• A、LOCK TABLE emp IN SHARE MODE；
• B、LOCK TABLE emp IN EXCLUSIVE MODE；
• C、UPDATE emp SET sal=sal*1.2 WHERE job=MANAGER；
• D、INSERT INTO emp（empno，ename） VALUES （1289，’Harry’）；
• E、SELECT ename FROM emp WHERE job=’CLERK’ FOR UPDATE OF empno；

第8题：

变压器的初、次级电流I₁、I₂和初、次级U₁、U₂之间的关系为（）。

• A、I₁/I₂＝U₁/U₂
• B、I₁/I₁＝U₂/U₁
• C、I₁/I₂＝U₂₂/U₁₂
• D、无明显规律

第9题：

第10题：

第11题：

第12题：

第13题：

第14题：

Given the following table definition: STOCK: item VARCHAR(30) status CHAR(1) quantity INT price DEC(7,2) If items are indicated to be out of stock by setting STATUS to NULL and QUANTITY and PRICE to zero, which of the following statements would be used to update the STOCK table to indicate that all the items whose description begins with the letter "S" are out of stock?（）

• A、UPDATE stock SET (status = NULL; quantity, price = 0) WHERE item LIKE S%
• B、UPDATE stock SET (status, quantity, price) = (NULL, 0, 0) WHERE item LIKE S%
• C、UPDATE stock SET status = NULL, SET quantity = 0, SET price = 0 WHERE item LIKE 'S%'
• D、UPDATE stock SET (status = NULL), (quantity = 0), (price = 0) WHERE item LIKE S%

第15题：

两个电阻R1、R2串联在电路中，则有（）。

• A、I1＞I2
• B、I1＜I2
• C、I1＝I2
• D、I1≠I2

第16题：

电流互感器的角误差，可用下式表示：Δfi%＝（）。其中K为电流互感器的额定变比，I1为一次绕组中的电流；I2为二次绕组中的电流。

• A、［（KI2～I1）／I1］100%；
• B、（I2～I1）100%／I1；
• C、I2～I1；
• D、I2／I1。

第17题：

Given table T1 has column I1 containing the following data: I1 1 2 3 4 If the following sequence of SQL statements is applied within a single unit of work: UPDATE t1 SET i1 = 3 WHERE i1 = 2; S AVEPOINT s1 ON ROLLBACK RETAIN CURSORS; UPDATE t1 SET i1 = 5 WHERE i1 = 3; SAVEPOINT s2 ON ROLLBACK RETAIN CURSORS;INSERT INTO t1 (i1) VALUES (6); ROLLBACK TO SAVEPOINT s1; UPDATE t1 SET i1 = 2 WHERE i1 = 4; COMMIT; What is the expected sequence of values returned from?（） SELECT i1 FROM t1 ORDER BY i1

• A、1, 2, 3, 3
• B、1, 2, 2, 4
• C、1, 2, 3, 3, 6
• D、1, 2, 2, 5, 6

第18题：

View the following SQL statements：   Transaction T1 INSERT INTO hr.regions VALUES （5，’Pole’）；COMMIT；  Transaction T2 UPDATE hr.regions SET region_name=’Poles’ WHERE region_id = 5； COMMIT；  Transaction T3 UPDATE hr.regions SET region_name=’North and South Poles’ WHERE region_id = 5；   You want to back out transaction T2.  Which option would you use？（）

• A、 It is possible，but transaction T3 also backs out.
• B、 It is possible with the NOCASCADE_FORCE option.
• C、 It is possible with the NONCONFLICT_ONLY option.
• D、 It is not possible because it has conflicts with transaction T3.

第19题：

User SCOTT executes the following command on the EMP table but has not issued COMMIT， ROLLBACK， orany data definition language （DDL） command： SQL> SELECT ename FROM emp WHERE job=’CLERK’ FOR UPDATE OF empno； SCOTT has opened another session to work with the database instance.  Which three operations would waitwhen issued in SCOTT’s second session（）

• A、LOCK TABLE emp IN SHARE MODE；
• B、LOCK TABLE emp IN EXCLUSIVE MODE；
• C、UPDATE emp SET sal=sal*1.2 WHERE job=ANAGER？UPDATE emp SET sal=sal*1.2 WHERE job=？ANAGER？
• D、INSERT INTO emp（empno，ename） VALUES （1289，’Harry’）；
• E、SELECT ename FROM emp WHERE job=’CLERK’ FOR UPDATE OF empno

第20题：

浓度为1mol·kg^-1的CuSO₄浓度的离子强度I₁，浓度为1mol·kg^-1的NaCl浓度的离子强度I₂，那么I₁与I₂的关系为（）

• A、I₁=（1/2）I₂
• B、I₁=I₂
• C、I₁=4I₂
• D、I₁=2I₂

第21题：

第22题：

第23题：

第24题：