1. Which SELECT statement will get the result ‘elloworld’ from the string ‘HelloWorld’?
   A. SELECT SUBSTR( ‘HelloWorld’,1) FROM dual;
   B. SELECT INITCAP(TRIM (‘HelloWorld’, 1,1)) FROM dual;
   C. SELECT LOWER(SUBSTR(‘HelloWorld’, 1, 1) FROM dual;
   D. SELECT LOWER(SUBSTR(‘HelloWorld’, 2, 1) FROM dual;
   E. SELECT LOWER(TRIM (‘H’ FROM ‘HelloWorld’)) FROM dual;

ANS: E

2. Which two statements are true regarding the ORDER BY clause? (Choose two.)
   A. The sort is in ascending order by default.
   B. The sort is in descending order by default.
   C. The ORDER BY clause must precede the WHERE clause.
   D. The ORDER BY clause is executed on the client side.
   E. The ORDER BY clause comes last in the SELECT statement.
   F. The ORDER BY clause is executed first in the query execution.

ANS: A E

3. Which two tasks can you perform using only the TO_CHAR function? (Choose two.)
   A. convert 10 to ‘TEN’
   B. convert ‘10’ to 10
   C. convert ‘10’ to ‘10’
   D. convert ‘TEN’ to 10
   E. convert a date to a character expression
   F. convert a character expression to a date

ANS: C E

4. Which operator can be used with a multiple-row subquery?
   A. =
   B. LIKE
   C. BETWEEN
   D. NOT IN
   E. Is
   F. <>

ANS: D

5. Which three statements about subqueries are true? (Choose three.)
   A. A single row subquery can retrieve only one column and one row.
   B. A single row subquery can retrieve only one row but many columns
   C. A multiple row subquery can retrieve multiple rows and multiple columns.
   D. A multiple row subquery can be compared using the “>” operator.
   E. A single row subquery can use the IN operator.
   F. A multiple row subquery can use the “=” operator.

ANS: A D E

6. Based on the following conditions, which of the following will make a true condition?
   last_name LIKE Ma%

A. MADNESS
B. Man
C. MARY
D. mary
E. Mandy

ANS: B E

7. Which of the following SQL statements can calculate and return the absolute value of -33?

A. SELECT ABS(-33) “Absolute” FROM DUAL;
B. SELECT ABS(-33), Absolute FROM DUAL;
C. SELECT ABS("-33") Absolute FROM DUAL;

ANS: A

8. What does the following SQL script do?
   SELECT AVG(MAX(salary)) FROM employees GROUP BY department_id;

A. it has a syntax error, the AVG clause is not valid
B. it calculates the average of the maximum salaries of all the departments
C. it has a syntax error, the MAX clause is not valid
D. it has no error, but the GROUP BY clause is not effective
E. it has no error, but the AVG clause is not effective
F. it has no error, but the MAX clause is not effective

ANS: B

9. Which three SELECT statements display 2000 in the format "$2,000.00&quot;? (Choose three.) A. SELECT TO_CHAR(2000, &#x27;$#,###.##’) FROM dual;
   B. SELECT TO_CHAR(2000, ‘$0,000.00’) FROM dual;
   C. SELECT TO_CHAR(2000, ‘$9,999.00’) FROM dual;
   D. SELECT TO_CHAR(2000, ‘$9,999.99’) FROM dual;
   E. SELECT TO_CHAR(2000, ‘$2,000.00&#x27;) FROM dual; F. SELECT TO_CHAR(2000, &#x27;$N,NNN.NN’) FROM dual;

ANS: B C D

資料庫實戰
有三張表：
table dep（dep_id number(2), //部門編號
dep_name varchar2(10)) //部門名稱

table emp (emp_id number(6), //員工編號
emp_name varchar2(20), //員工名稱
dep_id number(2)) //部門編號

table busi(emp_id number(6), //員工編號
busi_id number(10), //業務編號
busi_status char(2), //業務狀態 1 正常 2 未生效 3 失效 4 刪除
busi_datetime date, //業務時間
busi_desc varchar2(10)) //業務描述
alter table busi add constraint PK_busi primary key (busi_id);

問題：
1． 完成一個 procedure，輸入 dep_id, 輸出該部門的員工數。並對該部門所有員工的業務記錄，按下列條件更新：
busi_datetime 早於 20010101 12:00:00 的，busi_status 置為 ‘刪除’
busi_datetime 早於 20020101 12:00:00 的，busi_status 置為 ‘失效’，
busi_datetime 在20020101 12:00:00 和 20030101 12:00:00 之間的，busi_datetime 時間修改為 原 busi_datetime ＋ 5 天
CREATE OR REPLACE PRODURE TT(NDEP_ID VARCHAR2)
AS
CURSOR TT IS SELECT EMP_ID,BUSI_DATETIME FROM BUSI T1,EMP T2 WHERE T1.EMP_ID = T2.EMP_ID AND T2.DEP_ID = NDEP_ID ;
BEGIN
FOR TNT IN TT LOOP
IF TNT.BUSI_DATETIME < TO_DATE(‘20010101 12:00:00’,’YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_STATUS = ‘刪除’ WHERE EMP_ID TNT.EMP_ID;
ELSE IF TNT.BUSI_DATETIME < TO_DATE(‘20020101 12:00:00’,’YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_STATUS = ‘失效’ WHERE EMP_ID TNT.EMP_ID;
ELSE IF TNT.BUSI_DATETIME < TO_DATE(‘20030101 12:00:00’,’YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_DATETIME = TNT.BUSI_DATETIME + 5 WHERE EMP_ID TNT.EMP_ID;
END IF;
COMMIT;
END LOOP
END

CREATE OR REPLACE PRODURE TT(NDEP_ID VARCHAR2)
AS
CURSOR TT IS SELECT EMP_ID,BUSI_DATETIME
FROM BUSI T1,EMP T2
WHERE T1.EMP_ID = T2.EMP_ID AND T2.DEP_ID = NDEP_ID ;
num1 number:=0;
BEGIN
/* SELECT count(*) into num1
FROM BUSI T1,EMP T2
WHERE T1.EMP_ID = T2.EMP_ID AND T2.DEP_ID = NDEP_ID ;
*/
FOR TNT IN TT LOOP
IF TNT.BUSI_DATETIME < TO_DATE(‘20010101 12:00:00’,‘YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_STATUS = ‘刪除’ WHERE EMP_ID TNT.EMP_ID;
ELSIF TNT.BUSI_DATETIME < TO_DATE(‘20020101 12:00:00’,‘YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_STATUS = ‘失效’ WHERE EMP_ID TNT.EMP_ID;
ELSIF TNT.BUSI_DATETIME < TO_DATE(‘20030101 12:00:00’,‘YYYY-MM-DD HH24:MI:SS’)
THEN
UPDATE BUSI SET BUSI_DATETIME = TNT.BUSI_DATETIME + 5 WHERE EMP_ID TNT.EMP_ID;
END IF;
COMMIT;
num1:=num1+1;
END LOOP;
dbms_output.put_line(num1);
END;

2． Table busi 有 1000000 萬記錄。有一句 sql：
select emp_id,busi_id,busi_datetime,busi_desc from busi where emp_id= :value1 and busi_status = :value2
執行異常頻繁，效率很差，請解釋該 SQL 的執行計劃。用什麼方法可以提高該 SQL 的執行效率？

Where 子句使用引數導致全表掃描，使用字元型進行比較
針對比較建立聯合索引

3．業務量增加，table busi 資料量急劇增加，每天增加 20 萬資料，又刪除該錶的歷史資料 10 萬，二個月後，上面的SQL執行效率極差。用什麼方法可以提高該 SQL 的執行效率？
定時分析，降低hwm高水位
按時間分割槽，定時物件統計收集