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[经验分享] ocp 1Z0-051 23-70题解析

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发表于 2015-6-17 10:31:55 | 显示全部楼层 |阅读模式
23. Examine thestructure proposed for the TRANSACTIONS table:

name Null Type

TRANS_ID NOT NULLNUMBER(6)

CUST_NAME NOT NULLVARCHAR2(20)

CUST_STATUS NOT NULLCHAR

TRANS_DATE NOT NULL DATE

TRANS_VALIDITY VARCHAR2

CUST_CREDIT_LIMIT NUMBER

Which statements aretrue regarding the creation and storage of data in the above table structure?

(Choose all that apply.)

A. The CUST_STATUScolumn would give an error.

B. The TRANS_VALIDITYcolumn would give an error.

C. The CUST_STATUScolumn would store exactly one character.

D. The CUST_CREDIT_LIMITcolumn would not be able to store decimal values.

E. The TRANS_VALIDITY columnwould have a maximum size of one character.

F. The TRANS_DATE columnwould be able to store day, month, century, year, hour, minutes, seconds,

and fractions ofseconds.

  Answer: BC
  解析:
引用官方文档:
  The default length for a CHAR column is 1 byte and themaximum allowed is 2000
  bytes. A 1-byte stringcan be inserted into a CHAR(10) column, but the string is
  blank-padded to 10 bytesbefore it is stored.
  所以C正确,A错误
  
  You mustspecify a maximum length for a VARCHAR2 column.This maximum must be
  at least 1 byte, althoughthe actual string stored is permitted to be a zero-length string
  ('').
  所以B正确,E错误
  
  引用官方文档的一个表格:
  Actual Data Specified AsStored As
  123.89 NUMBER 123.89
  
  测试:
  
  scott@ORCL>createtable zbcxy(id number);
  
  表已创建。
  
  scott@ORCL>insertinto zbcxy values(123.68);
  
  已创建 1 行。
  
  scott@ORCL>select *from zbcxy;
  
  ID
  ----------
  123.68
  
  D选项错误
  
  
  The DATE data typestores date and time information. Although date and time
  information can berepresented in both character and number data types, the DATE
  data type has specialassociated properties. For each DATE value, Oraclestores the
  followinginformation: year, month, day, hour, minute, and second.
  选项F错误
  
  
24. Examine thestructure proposed for the TRANSACTIONS table:

name Null Type

  TRANS_ID NOT NULL NUMBER(6)
CUST_NAME NOT NULLVARCHAR2(20)

CUST_STATUS NOT NULLVARCHAR2

TRANS_DATE NOT NULL DATE

TRANS_VALIDITY INTERVALDAY TO SECOND

CUST_CREDIT_VALUENUMBER(10)

Which two statements aretrue regarding the storage of data in the above table structure? (Choose two.)

A. The TRANS_DATE columnwould allow storage of dates only in the dd-mon-yyyy format.

B. The CUST_CREDIT_VALUEcolumn would allow storage of positive and negative integers.

C. The TRANS_VALIDITYcolumn would allow storage of a time interval in days, hours, minutes, and

seconds.

D. The CUST_STATUScolumn would allow storage of data up to the maximum VARCHAR2 size of 4,000

characters.

  Answer: BC
  解析:
A选项中可以使用to_char设置多种格式
  引用官方文档:
  The NUMBER data typestores zero as well as positive and negativefixed numbers with
  absolute values from 1.0x 10-130 to but not including 1.0 x 10126.
  所以B正确
  INTERVAL DAY TO SECONDstores a period of time in terms of days, hours,minutes,
  and seconds. This data type is useful for representing the precisedifference between
  two datetime values.
  所以C正确
  D选项根据上题可知,使用varchar类型,必须指定长度,所以D选项错误
  
  
  
25. You need to create atable with the following column specifications:

1. Employee ID (numericdata type) for each employee

2. Employee Name(character data type) that stores the employee name

3. Hire date, whichstores the date of joining the organization for each employee

4. Status (characterdata type), that contains the value 'ACTIVE' if no data is entered

5. Resume (characterlarge object [CLOB] data type), which contains the resume submitted by the

employee

Which is the correctsyntax to create this table?

A. CREATE TABLE EMP_1

(emp_id NUMBER(4),

emp_name VARCHAR2(25),

start_date DATE,

e_status VARCHAR2(10)DEFAULT 'ACTIVE',

resume CLOB(200));

B. CREATE TABLE 1_EMP

(emp_id NUMBER(4),

emp_name VARCHAR2(25),

start_date DATE,

emp_status VARCHAR2(10)DEFAULT 'ACTIVE',

resume CLOB);

  C. CREATE TABLE EMP_1
(emp_id NUMBER(4),

emp_name VARCHAR2(25),

start_date DATE,

emp_status VARCHAR2(10)DEFAULT "ACTIVE",

resume CLOB);

D. CREATE TABLE EMP_1

(emp_id NUMBER,

emp_name VARCHAR2(25),

start_date DATE,

emp_status VARCHAR2(10)DEFAULT 'ACTIVE',

resume CLOB);

  Answer: D
  解析:
  引用官方文档:
  The CLOB data typestores single-byte and multibyte character data. Both fixed-width
  and variable-widthcharacter sets are supported, and both use the database character set
  使用clob无需指定长度,所以A错
  B选项 表名不能以数字开头
  C选项 default 用单引号
  所以D正确
  
  
26. Which is the validCREATE TABLE statement?

A. CREATE TABLE emp9$#(emp_no NUMBER (4));

B. CREATE TABLE 9emp$#(emp_no NUMBER(4));

C. CREATE TABLE emp*123(emp_no NUMBER(4));

D. CREATE TABLE emp9$#(emp_no NUMBER(4), date DATE);

  Answer: A
  解析:
创建表时,表的名称必须是合法标示符,长度为1-30字节,并且以字母开头,可以包含字母,数字,下划线,美元符号和#,此外表名称不能与所属模式中其他对象同名,也不能是oracle数据库的保留字
  由此判断B和C错误
  D选项不能使用oracle中关键字作为属性名称
  所以A正确
  
  
27. Which two statementsare true regarding tables? (Choose two.)

A. A table name can beof any length.

B. A table can have anynumber of columns.

C. A column that has aDEFAULT value cannot store null values.

D. A table and a viewcan have the same name in the same schema.

E. A table and a synonymcan have the same name in the same schema.

F. The same table namecan be used in different schemas in the same database.

  Answer: EF
  根据上题所知,表名的长度在1-30字节,所以A选项错误
  B选项,测试:
  BEGIN
  FOR I IN 1..999 LOOP
  EXECUTE IMMEDIATE 'ALTERTABLE zbcxy ADD id' || I || ' NUMBER(1)';
  END LOOP;
  END;
  
  
  scott@ORCL>altertable zbcxy add id1000 number(1);
  alter table zbcxy addid1000 number(1)
  *
  第 1 行出现错误:
  ORA-01792: 表或视图中的最大列数为 1000
  可知oracle限制最大列数为1000,所以B选项错误
  
  C选项,测试:
  scott@ORCL>createtable zbcxy(name varchar(20) default 'zbcxy');
  
  表已创建。
  
  scott@ORCL>insertinto zbcxy values(' ');
  
  已创建 1 行。
  
  scott@ORCL>select *from zbcxy;
  

  NAME
  
  所以C选项错误
  
  D选项,一个模式下面的对象是不能同名的,所以D选项错误
  E选项,测试:
  scott@ORCL>createpublic synonym emp for emp;
  
  同义词已创建。
  scott@ORCL>createsynonym dept for dept;
  create synonym dept fordept
  *
  第 1 行出现错误:
  ORA-01471: 无法创建与对象同名的同义词
  这里题意估计是指的公共的
  所以E选项正确
  F选项,不同模式下可以有同名的对象
  
  
  
  
28. Which two statementsare true regarding constraints? (Choose two.)

A. A foreign key cannot containNULL values.

B. A column with theUNIQUE constraint can contain NULL values.

C. A constraint isenforced only for the INSERT operation on a table.

D. A constraint can bedisabled even if the constraint column contains data.

E. All constraints can bedefined at the column level as well as the table level.

  Answer: BD
  解析:
选项A,如果参照表中有空值,则外键也可以为空值,可以采用
  Insert into zbcxy valuesselecet ename from emp;这种方式将emp中ename的控制插入到zbcxy表中
  所以选项A是错误的
  
  B选项,很明显unique约束时可以是空值,这里就不演示测试了
  
  C选项,明显错误,不止insert ,执行update操作也是必须遵守约束的
  
  D选项,测试:
scott@ORCL>create table zbcxy(id number(4) constraint p_pk primary key);
  
  表已创建。
  
  scott@ORCL>insertinto zbcxy values(1);
  
  已创建 1 行。
  
  scott@ORCL>altertable zbcxy disable constraint p_pk;
  
  表已更改。
  所以D选项正确
  E选项,非空约束只能定义列级约束,所以E选项是错误的
  
  29. Which two statementsare true regarding constraints? (Choose two.)
A. A foreign key cannotcontain NULL values.

B. The column with aUNIQUE constraint can store NULLS .

C. A constraint isenforced only for an INSERT operation on a table.

D. You can have morethan one column in a table as part of a primary key.

  Answer: BD
  解析:
  A选项,由上题可知是错误的
  B选项,由上题可知是正确的
  C选项,由上题可知是错误的
  D选项,一个表中只能有虽然只有一个约束,但是可以建立一个联合主键约束,这样就有多列为主键约束,所以D选项正确
  
  
30. Evaluate thefollowing CREATE TABLE commands:

CREATE TABLE orders

(ord_no NUMBER(2)CONSTRAINT ord_pk PRIMARY KEY,

ord_date DATE,

cust_id NUMBER(4));

CREATE TABLE ord_items

(ord_no NUMBER(2),

item_no NUMBER(3),

qty NUMBER(3) CHECK (qtyBETWEEN 100 AND 200),

expiry_date date CHECK(expiry_date > SYSDATE),

CONSTRAINT it_pk PRIMARYKEY (ord_no,item_no),

CONSTRAINT ord_fkFOREIGN KEY(ord_no) REFERENCES orders(ord_no));

The above command failswhen executed. What could be the reason?

A. SYSDATE cannot beused with the CHECK constraint.

B. The BETWEEN clausecannot be used for the CHECK constraint.

C. The CHECK constraintcannot be placed on columns having the DATE data type.

D. ORD_NO and ITEM_NOcannot be used as a composite primary key because ORD_NO is also the

FOREIGN KEY.

  Answer: A
  解析:
  scott@ORCL>CREATETABLE ord_items
  2 (ord_no NUMBER(2),
  3 item_no NUMBER(3),
  4  qtyNUMBER(3) CHECK (qty BETWEEN 100 AND 200),
  5 expiry_date date CHECK (expiry_date > SYSDATE),
  6 CONSTRAINT it_pk PRIMARY KEY (ord_no,item_no),
  7 CONSTRAINT ord_fk FOREIGN KEY(ord_no) REFERENCES orders(ord_no));
  expiry_date date CHECK(expiry_date > SYSDATE),
  *
  第 5 行出现错误:
  ORA-02436: 日期或系统变量在 CHECK 约束条件中指定错误
  
  所以A选项正确
  
  
  
31. Evaluate thefollowing SQL commands:

SQL>CREATE SEQUENCEord_seq

INCREMENT BY 10

START WITH 120

MAXVALUE 9999

NOCYCLE;

SQL>CREATE TABLEord_items

(ord_no NUMBER(4)DEFAULTord_seq.NEXTVAL NOT NULL,

item_no NUMBER(3),

  qty NUMBER(3) CHECK (qtyBETWEEN 100 AND 200),
expiry_date date CHECK(expiry_date > SYSDATE),

CONSTRAINT it_pk PRIMARYKEY (ord_no,item_no),

CONSTRAINT ord_fkFOREIGN KEY(ord_no) REFERENCES orders(ord_no));

The command to create atable fails. Identify the reason for the SQL statement failure? (Choose allthat

apply.)

A. You cannot useSYSDATE in the condition of a CHECK constraint.

B. You cannot use theBETWEEN clause in the condition of a CHECK constraint.

C. You cannot use theNEXTVAL sequence value as a DEFAULT value for a column.

D. You cannot use ORD_NOand ITEM_NO columns as a composite primary key because ORD_NO is

also the FOREIGN KEY.

Answer: AC

  解析:
  scott@ORCL>CREATETABLE ord_items
  2 (ord_no NUMBER(4)DEFAULT ord_seq.NEXTVAL NOT NULL,
  3 item_no NUMBER(3),
  4  qtyNUMBER(3) CHECK (qty BETWEEN 100 AND 200),
  5 expiry_date date CHECK (expiry_date > SYSDATE),
  6 CONSTRAINT it_pk PRIMARY KEY (ord_no,item_no),
  7 CONSTRAINT ord_fk FOREIGN KEY(ord_no) REFERENCES orders(ord_no));
  (ord_no NUMBER(4)DEFAULTord_seq.NEXTVAL NOT NULL,
  *
  第 2 行出现错误:
  ORA-00984: 列在此处不允许
  由上题可知A选项正确,B,D选项错误,经上面测试,C选项正确
  
  
  
32. Which CREATE TABLEstatement is valid?

A. CREATE TABLEord_details

(ord_no NUMBER(2)PRIMARY KEY,

item_no NUMBER(3)PRIMARY KEY,

ord_date DATE NOT NULL);

B. CREATE TABLEord_details

(ord_no NUMBER(2)UNIQUE, NOT NULL,

item_no NUMBER(3),

ord_date DATE DEFAULTSYSDATE NOT NULL);

C. CREATE TABLEord_details

(ord_no NUMBER(2) ,

item_no NUMBER(3),

ord_date DATE DEFAULTNOT NULL,

CONSTRAINT ord_uq UNIQUE(ord_no),

CONSTRAINT ord_pkPRIMARY KEY (ord_no));

D. CREATE TABLEord_details

(ord_no NUMBER(2),

item_no NUMBER(3),

ord_date DATE DEFAULTSYSDATE NOT NULL,

CONSTRAINT ord_pkPRIMARY KEY (ord_no, item_no));

  Answer: D
  解析:
  A选项:一个表中不能有两个主键
  B选项:约束那里语法错误
  C选项:default用法错误,以及一个列不能同时附加两个唯一约束,测试:
  scott@ORCL>create table zbcxy(id number(2),
  2  constraint p_idu unique(id),
  3  constraint p_idk primary key(id)
  4  );
constraint p_idu unique(id),
                 *
第 2 行出现错误:
ORA-02261: 表中已存在这样的唯一关键字或主键

  D选项正确
  
  
33. You want to createan ORD_DETAIL table to store details for an order placed having the following

  business requirement:
1) The order ID will beunique and cannot have null values.

2) The order date cannothave null values and the default should be the current date.

3) The order amountshould not be less than 50.

4) The order status willhave values either shipped or not shipped.

5) The order paymentmode should be cheque, credit card, or cash on delivery (COD).

Which is the valid DDLstatement for creating the ORD_DETAIL table?

A. CREATE TABLEord_details

(ord_id NUMBER(2)CONSTRAINT ord_id_nn NOT NULL,

ord_date DATE DEFAULTSYSDATE NOT NULL,

ord_amount NUMBER(5, 2)CONSTRAINT ord_amount_min

CHECK (ord_amount >50),

ord_status VARCHAR2(15)CONSTRAINT ord_status_chk

CHECK (ord_status IN('Shipped', 'Not Shipped')),

ord_pay_modeVARCHAR2(15) CONSTRAINT ord_pay_chk

CHECK (ord_pay_mode IN('Cheque', 'Credit Card',

'Cash On Delivery')));

B. CREATE TABLEord_details

(ord_id NUMBER(2)CONSTRAINT ord_id_uk UNIQUE NOT NULL,

ord_date DATE DEFAULTSYSDATE NOT NULL,

ord_amount NUMBER(5, 2)CONSTRAINT ord_amount_min

CHECK (ord_amount >50),

ord_status VARCHAR2(15)CONSTRAINT ord_status_chk

CHECK (ord_status IN('Shipped', 'Not Shipped')),

ord_pay_modeVARCHAR2(15) CONSTRAINT ord_pay_chk

CHECK (ord_pay_mode IN('Cheque', 'Credit Card',

'Cash On Delivery')));

C. CREATE TABLEord_details

(ord_id NUMBER(2)CONSTRAINT ord_id_pk PRIMARY KEY,

ord_date DATE DEFAULTSYSDATE NOT NULL,

ord_amount NUMBER(5, 2)CONSTRAINT ord_amount_min

CHECK (ord_amount >=50),

ord_status VARCHAR2(15)CONSTRAINT ord_status_chk

CHECK (ord_status IN('Shipped', 'Not Shipped')),

  ord_pay_modeVARCHAR2(15) CONSTRAINT ord_pay_chk
CHECK (ord_pay_mode IN('Cheque', 'Credit Card',

'Cash On Delivery')));

D. CREATE TABLEord_details

(ord_id NUMBER(2),

ord_date DATE NOT NULLDEFAULT SYSDATE,

ord_amount NUMBER(5, 2)CONSTRAINT ord_amount_min

CHECK (ord_amount >=50),

ord_status VARCHAR2(15)CONSTRAINT ord_status_chk

CHECK (ord_status IN('Shipped', 'Not Shipped')),

ord_pay_modeVARCHAR2(15) CONSTRAINT ord_pay_chk

CHECK (ord_pay_mode IN('Cheque', 'Credit Card',

'Cash On Delivery')));

  Answer: C
  解析:
  根据题目第一句话:The order ID willbe unique and cannot have null values
  只有主键才能满足这个条件,unique是可以为空值的
  正确答案只能为C选项
  
34. You created anORDERS table with the following description:

name Null Type

ORD_ID NOT NULLNUMBER(2)

CUST_ID NOT NULLNUMBER(3)

ORD_DATE NOT NULL DATE

ORD_AMOUNT NOT NULLNUMBER (10,2)

You inserted some rowsin the table. After some time, you want to alter the table by creating the

PRIMARY KEY constrainton the ORD_ID column. Which statement is true in this scenario?

A. You cannot have twoconstraints on one column.

B. You cannot add aprimary key constraint if data exists in the column.

C. The primary keyconstraint can be created only at the time of table creation .

D. You can add theprimary key constraint even if data exists, provided that there are noduplicate

values.

  Answer: D
  解析:
  题目意思是在一个已有数据的表中,将第一列改为主键约束,只要该列没有重复值是可以更改的,测试:
scott@ORCL>select * from zbcxy;
  
  ID
  ----------
  1
  2
  3
  scott@ORCL>altertable zbcxy add constraint p_pk primary key(id);
  
  表已更改。
  如果表中存在相同列:
scott@ORCL>select * from zbcxy;
  
  ID
  ----------
  1
  2
  3
  2
  
  scott@ORCL>altertable zbcxy add constraint p_pk primary key(id);
  alter table zbcxy addconstraint p_pk primary key(id)
  *
  第 1 行出现错误:
  ORA-02437: 无法验证 (SCOTT.P_PK) - 违反主键
  
  所以选项D正确
  
35. Which two statementsare true regarding constraints? (Choose two.)

A. A table can have onlyone primary key and one foreign key.

B. A table can have onlyone primary key but multiple foreign keys.

C. Only the primary keycan be defined at the column and table levels.

D. The foreign key andparent table primary key must have the same name.

E. Both primary key andforeign key constraints can be defined at both column and table levels.

Answer: BE

解析:

一个表中只能有一个主键约束,多个外键约束,除了非空约束不能定位表级约束,其他约都可以,外键只需数据类型一样,无需字段名一样

所以选项为BE



36. Examine thefollowing SQL commands:

SQL>CREATE TABLEproducts (

prod_id NUMBER(3) CONSTRAINTp_ck CHECK (prod_id > 0),

prod_name CHAR(30),

prod_qty NUMBER(6),

CONSTRAINT p_name NOTNULL,

CONSTRAINT prod_pkPRIMARY KEY (prod_id));

SQL>CREATE TABLEwarehouse (

warehouse_id NUMBER(4),

roomno NUMBER(10)CONSTRAINT r_id CHECK(roomno BETWEEN 101 AND 200),

location VARCHAR2(25),

prod_id NUMBER(3),

CONSTRAINT wr_pr_pkPRIMARY KEY (warehouse_id,prod_id),

CONSTRAINT prod_fkFOREIGN KEY (prod_id) REFERENCES products(prod_id));

Which statement is trueregarding the execution of the above SQL commands?

A. Both commands executesuccessfully.

B. The first CREATETABLE command generates an error because the NULL constraint is not valid.

C. The second CREATETABLE command generates an error because the CHECK constraint is not valid.

D. The first CREATE TABLEcommand generates an error because CHECK and PRIMARY KEY

constraints cannot beused for the same column.

E. The first CREATETABLE command generates an error because the column PROD_ID cannot be used

in the PRIMARY KEY andFOREIGN KEY constraints.

Answer: B

解析:

非空约束不能作为表级约束,所以B选项正确



37. You issued thefollowing command to drop the PRODUCTS table:

SQL> DROP TABLEproducts;

What is the implicationof this command? (Choose all that apply.)

A. All data along withthe table structure is deleted.

B. The pendingtransaction in the session is committed.

C. All indexes on thetable will remain but they are invalidated.

D. All views andsynonyms will remain but they are invalidated.

E. All data in the tableare deleted but the table structure will remain.

Answer: ABD

解析:

引用官方文档:
table

Specify the name of the table to be dropped. OracleDatabase automatically performs

the following operations:

■ All rows from the table are dropped.

■ All table indexes and domain indexesare dropped, as well as any triggers defined

on the table, regardless of who created them or whoseschema contains them. If

table is partitioned, then any corresponding local indexpartitions are also

dropped.

If the table is a base table for a view, a container or master table of a materialized

view, or if it is referenced in a stored procedure,function, or package, then the

database invalidates these dependent objects but does not drop them. You cannot

use these objects unless you re-create the table or dropand re-create the objects so

that they no longer depend on the table.


当然oracle使用drop删除是数据和表结构一起删除,delete是只删除数据,当前和该表的事务也应当马上提交



38. Which two statementsare true regarding views? (Choose two.)

A. A simple view in which column aliases have been usedcannot be updated.

B. Rows cannot bedeleted through a view if the view definition contains the DISTINCT keyword.

C. Rows added through aview are deleted from the table automatically when the view is dropped.

D. The OR REPLACE optionis used to change the definition of an existing view without dropping and

re-creating it.

E. The WITH CHECK OPTIONconstraint can be used in a view definition to restrict the columns

displayed through theview.

Answer: BD

解析:

引用官方文档:

Specify names for the expressions selected by the definingquery of the view. The

number of aliases must match the number of expressionsselected by the view. Aliases

must follow the rules for naming Oracle Database schemaobjects. Aliases must be

unique within the view.

If you omit the aliases, then the database derives themfrom the columns or column

aliases in the query. For this reason, you must usealiases if the query contains

expressions rather than only column names. Also, you mustspecify aliases if the view

definition includes constraints.

所以选项A错误


You cannot delete from a view except through INSTEAD OFtriggers if the defining

query of the view contains one of the followingconstructs:

A set operator

A DISTINCT operator

An aggregate or analytic function

A GROUP BY, ORDER BY, MODEL, CONNECT BY, or START WITHclause

A collection expression in a SELECT list

A subquery in a SELECT list

A subquery designated WITH READ ONLY

Joins, with some exceptions, as documented in OracleDatabase Administrator's

Guide

所以B选项正确


对视图操作最终会转换对基表操作,所以之前在视图上的操作,视图被删除之后,依然会保留在表上

所以C选项错误



Specify OR REPLACE to re-create the view if it alreadyexists. You can use this clause to

change the definition of an existing view withoutdropping, re-creating, and

regranting object privileges previously granted on it.

所以D选项正确


Specify WITH CHECK OPTION to indicate that Oracle

Database prohibits any changes to the table or view thatwould produce rows that are

not included in the subquery. When used in the subqueryof a DML statement, you

can specify this clause in a subquery in the FROM clausebut not in subquery in the

WHERE clause

所以E选项错误


39. Evaluate thefollowing command:

CREATE TABLE employees

(employee_id NUMBER(2)PRIMARY KEY,

last_name VARCHAR2(25)NOT NULL,

department_idNUMBER(2)NOT NULL,

job_id VARCHAR2(8),

salary NUMBER(10,2));

You issue the followingcommand to create a view that displays the IDs and last names of the salesstaff

in the organization:

CREATE OR REPLACE VIEWsales_staff_vu AS4 ? 4;

SELECT employee_id,last_name,job_id4 ? 4;

FROM employees4 ? 4;

WHERE job_id LIKE'SA_%'4 ? 4;

WITH CHECK OPTION;

Which two statements aretrue regarding the above view? (Choose two.)

A. It allows you toinsert rows into the EMPLOYEES table .

B. It allows you todelete details of the existing sales staff from the EMPLOYEES table.

C. It allows you toupdate job IDs of the existing sales staff to any other job ID in the EMPLOYEEStable.

D. It allows you to insertIDs, last names, and job IDs of the sales staff from the view if itis used in

multitable INSERTstatements.

Answer: BD

解析:
A选项,因为视图只有employee_id, last_name,job_id三个字段,无法进行插入操作,因为基表中的department_id是不允许为空的,而在视图中又不能指定department_id的值

所以A选项错误


B选项中,因为有创建视图时指定了last_name字段,所以视图可以根据last_name删除基表中数据

所以B选项正确


C选项,因为视图创建时,指定了WHERE job_id LIKE 'SA_%'4 ? 4;

WITH CHECK OPTION; 所以更改job_id也只能是'SA_%'4 ? 4这种格式

所以C选项错误


D选项 暂时不知道怎么实现



40. View the Exhibit toexamine the description for the SALES and PRODUCTS tables.

You want to create aSALE_PROD view by executing the following SQL statement:

CREATE VIEW sale_prod

AS SELECT p.prod_id,cust_id, SUM(quantity_sold) "Quantity" , SUM(prod_list_price)"Price"

FROM products p, sales s

WHERE p.prod_id=s.prod_id

GROUP BY p.prod_id,cust_id;

Which statement is trueregarding the execution of the above statement?

DSC0000.jpg

A. The view will becreated and you can perform DML operations on the view.

B. The view will becreated but no DML operations will be allowed on the view.

C. The view will not becreated because the join statements are not allowed for creating a view.

D. The view will not becreated because the GROUP BY clause is not allowed for creating a view.

Answer: B

  解析:该视图为两个表连接的结果,所以不能dml操作的,因为做了相应的操作视图不知道最后应将操作转换为那个表
  所以正确选项为B
  
41. Which two statementsare true regarding views? (Choose two.)

A. A subquery thatdefines a view cannot include the GROUP BY clause.

B. A view that iscreated with the subquery having the DISTINCT keyword can be updated.

C. A view that iscreated with the subquery having the pseudo column ROWNUM keyword cannot

be updated.

D. A data manipulationlanguage ( DML) operation can be performed on a view that is created with

  the subquery having allthe NOT NULL columns of a table.
  Answer: CD
  解析:
  由上题可知,A选项错误
  
You cannot delete from a view except through INSTEAD OFtriggers if the defining

query of the view contains one of the following constructs:

A set operator

A DISTINCT operator

An aggregate or analytic function

A GROUP BY, ORDER BY, MODEL, CONNECT BY, or START WITHclause

A collection expression in a SELECT list

A subquery in a SELECT list

A subquery designated WITH READ ONLY

Joins, with some exceptions, as documented in OracleDatabase Administrator's

Guide

所以B选项错误



C选项,rownum当然不可以被修改不管是在视图中,还是在表中

所以C选项正确


D选项,基表中如果没有非空约束,不管视图中的字段有多少,都可以进行操作,视图中没有的字段在基表中都默认为空

所以D选项正确



42. Which threestatements are true regarding views? (Choose three.)

A. Views can be createdonly from tables.

B. Views can be createdfrom tables or other views.

C. Only simple views canuse indexes existing on the underlying tables.

D. Both simple andcomplex views can use indexes existing on the underlying tables.

E. Complex views can becreated only on multiple tables that exist in the same schema.

F. Complex views can becreated on multiple tables that exist in the same or different schemas.

Answer: BDF

解析:
视图是可以根据视图创建的,所以A选项错误,B选项正确

C选项,复杂视图做一些操作时也可以使用基表中的索引

这里说明一下简单视图和复杂视图的定义:
简单视图:数据来源于基表,不包含函数,分组等,可以直接记性dml操作

复杂视图:来源于一个表或者多个表,可以包含连接,函数,分组等,能否直接进行dml操作取决于视图的具体定义

所以D选项正确


创建视图时候,只要指定该表属于哪个模式,是可以跨模式创建视图的,所以E选项错误

F选项正确



43. Evaluate thefollowing CREATE SEQUENCE statement:

CREATE SEQUENCE seq1

START WITH 100

INCREMENT BY 10

MAXVALUE 200

CYCLE

NOCACHE;

The SEQ1 sequence hasgenerated numbers up to the maximum limit of 200. You issue the following

SQL statement:

SELECT seq1.nextval FROMdual;

What is displayed by theSELECT statement?

A. 1

B. 10

C. 100

D. an error

Answer: A

解析:
The SEQ1 sequence hasgenerated numbers up to the maximum limit of 200

这里已经说明序列已经达到最大值了,因为该序列循环,没有指定最小值,所以将会从1开始,测试:



scott@ORCL>CREATE SEQUENCE seq1
  2  START WITH 100
  3  INCREMENT BY 10
  4  MAXVALUE 200
  5  CYCLE
  6  NOCACHE;


序列已创建。


scott@ORCL>BEGIN
  2  FOR I IN 1..100 LOOP
  3  insert into zbcxy values(seq1.nextval);
  4  END LOOP;
  5  END;
  6  /


PL/SQL 过程已成功完成。


scott@ORCL>select * from zbcxy;


        ID
----------
       110
       120
       130
       140
       150
       160
       170
       180
       190
       200
         1
        11
        21
        31
        41
        51
        61
        71
        81
        91



44. View the Exhibit andexamine the structure of the ORD table.

Evaluate the followingSQL statements that are executed in a user session in the specified order:

CREATE SEQUENCE ord_seq;

SELECT ord_seq.nextval

FROM dual;

INSERT INTO ord

VALUES (ord_seq.CURRVAL,'25-jan-2007',101);

UPDATE ord

SET ord_no=ord_seq.NEXTVAL

WHERE cust_id =101;

What would be theoutcome of the above statements?

DSC0001.jpg

A. All the statementswould execute successfully and the ORD_NO column would contain the value 2 for

the CUST_ID 101.

B. The CREATE SEQUENCEcommand would not execute because the minimum value and maximum

value for the sequencehave not been specified.

C. The CREATE SEQUENCEcommand would not execute because the starting value of the sequence

and the increment valuehave not been specified.

D. All the statementswould execute successfully and the ORD_NO column would have the value 20 for

the CUST_ID 101 becausethe default CACHE value is 20.

Answer: A

这里主要考察oracle默认队列的一些值,测试:
scott@ORCL>create sequence zbcxy;


序列已创建。


scott@ORCL>select zbcxy.currval from dual;

select zbcxy.currval from dual

                         *

第 1 行出现错误:

ORA-08002: 序列 ZBCXY.CURRVAL 尚未在此会话中定义



scott@ORCL>select zbcxy.nextval from dual;


   NEXTVAL

----------

         1

  
  可以看出序列默认的开始值为0,并且以1增长,最大值为:
Specify NOMAXVALUE to indicate a maximum value of 1028-1 for an
  ascending sequence or -1for a descending sequence. This is the default
  并且:nocycle
  Specify NOCYCLE toindicate that the sequence cannot generate more
  values after reachingits maximum or minimum value. This is the default.
  
  所以正确答案为A
  
  
45. Which two statementsare true about sequences created in a single instance database? (Choose

two.)

A. The numbers generatedby a sequence can be used only for one table.

B. DELETE would remove a sequence from the database.

C. CURRVAL is used torefer to the last sequence number that has been generated.

D. When the MAXVALUElimit for a sequence is reached, you can increase the MAXVALUE limit by using

the ALTER SEQUENCEstatement.

E. When a databaseinstance shuts down abnormally, the sequence numbers that have been cached but

not used would beavailable once again when the database instance is restarted.

  Answer: CD
  解析:
  一个序列可以被多个表使用,所以A选项错误
  
  B选项,删除序列:
scott@ORCL>drop sequence zbcxy;
  
  序列已删除。
  
  C选项,当前值就是最后序列最后一次生成的值
  
  D选项:
  
  scott@ORCL>altersequence zbcxy maxvalue 10;
  
  序列已更改。
  
  E选项:
Specify NOCACHE to indicate that values of the sequence are not
  preallocated. If youomit both CACHE and NOCACHE, then the database caches 20
  sequence numbers by default.
  
  
46. Which statements arecorrect regarding indexes? (Choose all that apply.)

A. When a table isdropped, the corresponding indexes are automatically dropped.

B. A FOREIGN KEYconstraint on a column in a table automatically creates a nonunique index.

C. A nondeferrablePRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a unique

index.

D. For each datamanipulation language (DML) operation performed, the corresponding indexes are

automatically updated.

  Answer: ACD
  解析:
  引用官方文档:
  All table indexes anddomain indexes are dropped, as well as any triggers defined
  on the table, regardlessof who created them or whose schema contains them. If
  table is partitioned,then any corresponding local index partitions are also
  dropped.
  所以A选项正确
  
  B选项,外键不自动创建索引,主键和唯一约束自动创建约束
  
  C选项 主键和唯一性约束自动创建索引,正确
  
  D选项 执行dml操作,索引自动更新,正确
  
  
  47. View the Exhibit andexamine the structure of ORD and ORD_ITEMS tables.
The ORD_NO column isPRIMARY KEY in the ORD table and the ORD_NO and ITEM_NO columns are

composite PRIMARY KEY inthe ORD_ITEMS table.

  Which two CREATE INDEXstatements are valid? (Choose two.)
DSC0002.jpg
A. CREATE INDEX ord_idx1

ON ord(ord_no);

B. CREATE INDEX ord_idx2

ON ord_items(ord_no);

C. CREATE INDEX ord_idx3

ON ord_items(item_no);

D. CREATE INDEX ord_idx4

ONord,ord_items(ord_no, ord_date,qty);

  Answer: BC
  解析:
主键自动创建索引,所以A选项错误
  B选项和C选项,因为ord_no和item_no是联合主键,所以可以为它们单独创建索引
D选项:
CREATE INDEX ord_idx4

ON ord,ord_items(ord_no,ord_date,qty);

  相当于创建了ord_no,ord_no和ord_date,ord_no和ord_date和qty三个索引
  因为ord_no和ord_date索引由ord_no和ord_date联合主键自动创建
  所以D选项错误
  
  
48. Which two statementsare true regarding indexes? (Choose two.)

A. They can be createdon tables and clusters.

B. They can be createdon tables and simple views.

C. You can create onlyone index by using the same columns.

D. You can create morethan one index by using the same columns if you specify distinctly different

combinations of thecolumns.

  Answer: AD
  解析:
索引可以表和clusters上面创建,所以A选项正确
  索引是不能在视图上创建的,所以B选项错误
  由上题D选项可得,C选项错误,D选项正确
  
49. The ORDERS tablebelongs to the user OE. OE has granted the SELECT privilege on the ORDERS

table to the user HR.

Which statement wouldcreate a synonym ORD so that HR can execute the following query successfully?

SELECT * FROM ord;

A. CREATE SYNONYM ordFOR orders; This command is issued by OE.

B. CREATE PUBLIC SYNONYMord FOR orders; This command is issued by OE.

  C. CREATE SYNONYM ordFOR oe.orders; This command is issued by the database administrator.
D. CREATE PUBLIC SYNONYMord FOR oe.orders; This command is issued by the database

administrator.

  Answer: D
  解析:
  由管理员创建的公有同义词,被用户组public所拥有,数据库所有用户都可以使用共有同义词
  所以选项D正确
  
  
  
50. SLS is a privatesynonym for the SH.SALES table.

The user SH issues thefollowing command:

DROP SYNONYM sls;

Which statement is trueregarding the above SQL statement?

A. Only the synonymwould be dropped.

B. The synonym would bedropped and the corresponding table would become invalid.

C. The synonym would bedropped and the packages referring to the synonym would be dropped.

D. The synonym would bedropped and any PUBLIC synonym with the same name becomes invalid.

  Answer: A
  解析:
  同义词就像一个指针指向它的对象,如果删除同义词,对该对象毫无影响
  详解见我的文章:
http://blog.iyunv.com/zbdba/article/details/16938969
  所以选项A正确
  
  
51. Which statement istrue regarding synonyms?

A. Synonyms can becreated only for a table.

B. Synonyms are used toreference only those tables that are owned by another user.

C. A public synonym anda private synonym can exist with the same name for the same table.

D. The DROP SYNONYMstatement removes the synonym, and the table on which the synonym has

been created becomesinvalid.

  Answer: C
  解析:
A选项,除了表,还可以为其他对象创建同义词,引用官方文档:
  Use the CREATE SYNONYMstatement to create a synonym, which is an alternative
  name for a table, view,sequence, operator, procedure, stored function, package,
  materialized view, Javaclass schema object, user-defined object type, or another
  synonym. A synonymplaces a dependency on its target object and becomes invalid if
  the target object is changedor dropped
  
  B选项,引用官方文档:
Synonyms provide both data independence and location transparency. Synonyms
  permit applications tofunction without modification regardless of which user owns
  the table or view andregardless of which database holds the table or view. However,
  synonyms are not asubstitute for privileges on database objects. Appropriate
  privileges must begranted to a user before the user can use the synonym
  
  C选项,测试:
  scott@ORCL>createsynonym synonmy_emp for emp;
  
  同义词已创建。
  
  scott@ORCL>createpublic synonym synonmyz_emp for emp;
  
  同义词已创建,
  所以C选项正确
  
  D选项,由上题可知,删除同义词对对象毫无影响
  
  
52. View the Exhibit andexamine the structure of the PRODUCTS table.

Using the PRODUCTStable, you issue the following query to generate the names, current list price,

and discounted listprice for all those products whose list price falls below $10 after a discountof 25% is

applied on it.

SQL>SELECT prod_name,prod_list_price,

prod_list_price -(prod_list_price * .25) "DISCOUNTED_PRICE"

FROM products

WHERE discounted_price< 10;

The query generates anerror.

  What is the reason forthe error?
DSC0003.jpg
  
A. The parenthesisshould be added to enclose the entire expression.

B. The double quotationmarks should be removed from the column alias.

C. The column aliasshould be replaced with the expression in the WHERE clause.

D. The column aliasshould be put in uppercase and enclosed with in double quotation marks in the

WHERE clause.

  Answer: C
  解析:
  Where 后面的条件是不能用别名的,可以直接使用前面的那个表达式,测试:
scott@ORCL>select sal&#43;1000 &quot;zbcxy&quot; from emp where zbcxyselect *from emp where ename between 'A' and 'D';
  
  EMPNO ENAME      JOB              MGR HIREDATE              SAL       COMM    DEPTNO
  ---------- ------------------- ---------- -------------- ---------- ---------- ----------
  7499 ALLEN      SALESMAN        7698 20-2月 -81           1600        160         30
  7698 BLAKE      MANAGER         7839 01-5月 -81       3324.24                    30
  7782 CLARK      MANAGER         7839 09-6月 -81          2450                    10
  7876 ADAMS      CLERK           7788 23-5月 -87          1100                    20
  输出第一个字母为A到D范围的员工
  
  
55. Evaluate thefollowing two queries:

SQL> SELECTcust_last_name, cust_city

FROM customers

WHERE cust_credit_limitIN (1000, 2000, 3000);

SQL> SELECTcust_last_name, cust_city

FROM customers

  WHERE cust_credit_limit= 1000 OR cust_credit_limit = 2000 OR
cust_credit_limit =3000;

Which statement is trueregarding the above two queries?

A. Performance wouldimprove in query 2.

B. Performance woulddegrade in query 2.

C. There would be nochange in performance.

D. Performance wouldimprove in query 2 only if there are null values in the CUST_CREDIT_LIMIT

column.

  Answer: C
  解析:
  这两种写法没什么差别,都需要和三个&#20540;一一比较
  
  
  
56. View the Exhibit andexamine the structure of the PROMOTIONS table.

Using the PROMOTIONStable, you need to find out the names and cost of all the promos done on 'TV'

and 'internet' thatended in the time interval 15th March '00 to 15th October '00.

Which two queries wouldgive the required result? (Choose two.)

DSC0004.jpg

A. SELECT promo_name,promo_cost

  FROM promotions
A. SELECT promo_name,promo_cost

FROM promotions

WHERE promo_category IN('TV', 'internet') AND

promo_end_date BETWEEN'15-MAR-00' AND '15-OCT-00';

B. SELECT promo_name,promo_cost

FROM promotions

WHERE promo_category ='TV' OR promo_category ='internet' AND

promo_end_date>='15-MAR-00' OR promo_end_date ='15-MAR-00' AND promo_end_date  SELECT part_code

FROM spares

WHERE part_code LIKE'%\%_WQ12%' ESCAPE '\';

  Which statement is trueregarding the outcome of the above query?
A. It produces an error.

B. It displays allvalues.

C. It displays only thevalues A%_WQ123 and AB_WQ123 .

D. It displays only thevalues A%_WQ123 and A%BWQ123 .

E. It displays only thevalues A%BWQ123 and AB_WQ123.

  Answer: D
  解析:
  scott@ORCL>select *from zbcxy;
  
  NAME
  ------------------------------
  A%_WQ123
  A%BWQ123
  AB_WQ123
  
  scott@ORCL>SELECTname
  2  FROMzbcxy
  3 WHERE name LIKE '%\%_WQ12%' ESCAPE '\';
  
  NAME
  ------------------------------
  A%_WQ123
  A%BWQ123
  
  所以正确选项为D
  
  
  
59. View the Exhibit andexamine the data in the PRODUCTS table.

You need to displayproduct names from the PRODUCTS table that belong to the 'Software/Other '

category with minimumprices as either $2000 or $4000 and no unit of measure.

You issue the followingquery:

SQL>SELECT prod_name,prod_category, prod_min_price

FROM products

WHERE prod_category LIKE'%Other%' AND (prod_min_price = 2000 OR

prod_min_price = 4000)AND prod_unit_of_measure  '';

  Which statement is trueregarding the above query?
DSC0005.jpg
A. It executessuccessfully but returns no result.

B. It executessuccessfully and returns the required result.

C. It generates an errorbecause the condition specified for PROD_UNIT_OF_MEASURE is not valid.

D. It generates an errorbecause the condition specified for the PROD_CATEGORY column is not valid.

  Answer: A
  解析:
  prod_unit_of_measure '',这里有问题 prod_unit_of_measureis null
  所以选项A正确
  
60. View the Exhibit andexamine the structure of CUSTOMERS table.

Evaluate the followingquery:

SQL>SELECT cust_id,cust_city

FROM customers

WHERE cust_first_nameNOT LIKE 'A_%g_%' AND

cust_credit_limitBETWEEN 5000 AND 15000 AND

cust_credit_limit NOT IN(7000, 11000) AND

cust_city NOT BETWEEN'A' AND 'B';

  Which statement is trueregarding the above query?
DSC0006.jpg
A. It executessuccessfully.

B. It produces an errorbecause the condition on the CUST_CITY column is not valid.

C. It produces an errorbecause the condition on the CUST_FIRST_NAME column is not valid.

D. It produces an errorbecause conditions on the CUST_CREDIT_LIMIT column are not valid.

  Answer: A
  解析:
它是能正确执行的,没有任何的语法错误,这里就不做测试了
  
  
61. View the Exhibit andexamine the structure of the PROMOTIONS table.

You need to generate areport of all promos from the PROMOTIONS table based on the following

conditions:

1. The promo name shouldnot begin with 'T' or 'N'.

2. The promo should costmore than $20000.

  3. The promo should haveended after 1st January 2001.
  Which WHERE clause wouldgive the required result?
DSC0007.jpg
A. WHERE promo_name NOTLIKE 'T%' OR promo_name NOT LIKE 'N%' AND promo_cost > 20000

AND promo_end_date >'1-JAN-01'

B. WHERE (promo_name NOTLIKE 'T%' AND promo_name NOT LIKE 'N%')OR promo_cost > 20000

OR promo_end_date >'1-JAN-01'

C. WHERE promo_name NOTLIKE 'T%' AND promo_name NOT LIKE 'N%' AND promo_cost > 20000

AND promo_end_date >'1-JAN-01'

D. WHERE (promo_name NOTLIKE '%T%' OR promo_name NOT LIKE '%N%') AND(promo_cost >

20000 AND promo_end_date> '1-JAN-01')

  Answer: C
  解析:
根据题意,姓名第一个字母中既不能包含T字母也不能包含N字母
  所以A和D选项错误
  B选项的 or应该换为and条件,所有条件都必须满足,不是只需要满足其中一个
  所以正确答案为C
  
  
  
62. View the E xhibitand examine the structure of the CUSTOMERS table.

You want to generate areport showing the last names and credit limits of all customers whose lastnames

start with A, B, or C,and credit limit is below 10, 000.

Evaluate the followingtwo queries:

SQL> SELECTcust_last_name, cust_credit_limit FROM customers

WHERE(UPPER(cust_last_name) LIKE 'A%' OR

UPPER(cust_last_name)LIKE 'B%' OR UPPER(cust_last_name) LIKE 'C%')

AND cust_credit_limit< 10000;

SQL>SELECTcust_last_name, cust_credit_limit FROM customers

WHEREUPPER(cust_last_name) BETWEEN 'A' AND 'C'

AND cust_credit_limit< 10000;

  Which statement is trueregarding the execution of the above queries?
DSC0008.jpg
A. Only the first querygives the correct result.

B. Only the second querygives the correct result.

C. Both executesuccessfully and give the same result.

D. Both executesuccessfully but do not give the required result.

  Answer: A
  解析:
  BETWEEN 'A' AND 'C'中的结果不包括C开头的
  所以只有A选项是正确的
  
  
63. View the E xhibitand examine the structure of the PRODUCTS table.

You want to display onlythose product names with their list prices where the list price is at leastdouble

the minimum price. Thereport should start with the product name having the maximum list pricesatisfying

this condition.

Evaluate the followingSQL statement:

SQL>SELECTprod_name,prod_list_price

FROM products

WHERE prod_list_price>= 2 * prod_min_price

Which ORDER BY clausescan be added to the above SQL statement to get the correct output?

  (Choose all that apply.)
DSC0009.jpg
A. ORDER BYprod_list_price DESC, prod_name;

B. ORDER BY(2*prod_min_price)DESC, prod_name;

C. ORDER BY prod_name,(2*prod_min_price)DESC;

D. ORDER BY prod_nameDESC, prod_list_price DESC;

  E. ORDER BYprod_list_price DESC, prod_name DESC;
  Answer: AE
  解析:
  根据题意prod_list_price降序并且先根据prod_list_price排序,所以A E正确
  
  
64. View the E xhibitand examine the data in the PROMO_CATEGORY and PROMO_COST columns of

the PROMOTIONS table.

Evaluate the followingtwo queries:

SQL>SELECT DISTINCTpromo_category to_char(promo_cost)&quot;code&quot;

FROM promotions

ORDER BY code;

SQL>SELECT DISTINCTpromo_category promo_cost &quot;code&quot;

FROM promotions

ORDER BY 1;

Which statement is true regardingthe execution of the above queries?

DSC00010.jpg
A. Only the first queryexecutes successfully.

B. Only the second queryexecutes successfully.

C. Both queries executesuccessfully but give different results.

  D. Both queries executesuccessfully and give the same result
  Answer: B
  解析:
  不能使用别名作为order by 后面的排序
  order by 1以第一列升序排列
  
  
  
65. View the Exhibit andexamine the structure of the CUSTOMERS table.

You have been asked toproduce a report on the CUSTOMERS table showing the customers details

sorted in descendingorder of the city and in the descending order of their income level in eachcity.

  Which query wouldaccomplish this task?
DSC00011.jpg
A. SELECT cust_city,cust_income_level, cust_last_name

FROM customers

ORDER BY cust_city desc,cust_income_level DESC ;

B. SELECT cust_city,cust_income_level, cust_last_name

FROM customers

ORDER BYcust_income_level desc, cust_city DESC;

C. SELECT cust_city,cust_income_level, cust_last_name

FROM customers

ORDER BY (cust_city,cust_income_level) DESC;

D. SELECT cust_city,cust_income_level, cust_last_name

FROM customers

ORDER BY cust_city,cust_income_level DESC;

  Answer: A
  解析:order by 每个列都可以指定desc or asc 因为题目都要求降序
  所以A选项正确,C选项语法错误
  
  
66. View the Exhibit andexamine the data in the COSTS table.

You need to generate areport that displays the IDs of all products in the COSTS table whose unitprice is

at least 25% more thanthe unit cost. The details should be displayed in the descending order of 25%of

the unit cost.

You issue the followingquery:

SQL>SELECT prod_id

FROM costs

WHERE unit_price >=unit_cost * 1.25

ORDER BY unit_cost *0.25 DESC;

  Which statement is trueregarding the above query?
DSC00012.jpg
A. It executes andproduces the required result.

B. It produces an errorbecause an expression cannot be used in the ORDER BY clause.

C. It produces an errorbecause the DESC option cannot be used with an expression in the ORDER BY

clause.

D. It produces an errorbecause the expression in the ORDER BY clause should also be specified in the

SELECT clause.

  Answer: A
  解析:表达式是可以作为order by后面的排序,所以正确答案为A
  
67. Which two statementsare true regarding the ORDER BY clause? (Choose two.)

A. It is executed firstin the query execution.

B. It must be the lastclause in the SELECT statement.

C. It cannot be used ina SELECT statement containin g a HAVING clause.

D. You cannot specify acolumn name followed by an expression in this clause.

E. You can specify acombination of numeric positions and column names in this clause.

  Answer: BE
  解析:
  选项A,应该是得到查询结果,然后在进行排序的
  选项B,order by 应该放在select 语句的最后,所以B选项正确
  选项C: scott@ORCL>select salfrom emp group by sal order by sal;
  
  SAL
  ----------
  950
  968
  1100
  1250
  所以C选项错误
  D选项,可以指定一个表达式在order by后面进行排序,根据上题可知,所以D选项正确
  E选项:
  scott@ORCL>selectename,sal from emp order by 1,sal desc;
  
  ENAME             SAL
  ---------- ----------
  ADAMS            1100
  ALLEN            1600
  BLAKE         3324.24
  CLARK            2450
  FORD             3000
  所以E选项正确
  
68. Which statement istrue regarding the default behavior of the ORDER BY clause?

A. In a character sort,the values are case- sensitive.

B. NULL values are notconsidered at all by the sort operation.

C. Only those columnsthat are specified in the SELECT list can be used in the ORDER BY clause.

D. Numeric values aredisplayed from the maximum to the minimum value if they have decimal positions.

  Answer: A
  解析:
  A选项,在字符排序是,区分大小写,这个是正确的
  B选项,这里oracle做排序的时候会考虑空&#20540;
  C选项,order by 排序时,不需要像group by 需要在select中指定,所以C选项错误
  D选项,默认都为升序
  
  
69. You need to generatea list of all customer last names with their credit limits from the CUSTOMERS

table. Those customerswho do not have a credit limit should appear last in the list.

Which two queries wouldachieve the required result? (Choose two.)

A. SELECTcust_last_name, cust_credit_limit

FROM customers

ORDER BYcust_credit_limit DESC ;

B. SELECTcust_last_name, cust_credit_limit

  FROM customers
ORDER BYcust_credit_limit;

C. SELECTcust_last_name, cust_credit_limit

FROM customers

ORDER BYcust_credit_limit NULLS LAST;

D. SELECTcust_last_name, cust_credit_limit

FROM customers

ORDER BY cust_last_name,cust_credit_limit NULLS LAST;

  Answer: BC
  解析:
  题意要求appear last inthe list,所以按照cust_credit_limit升序排序 order by 默认为升序,所以B选项正确   asc时, nulls last为默认 所以C选项正确
  
  
70. View the E xhibitand examine the structure of the PRODUCTS table.

You want to display onlythose product names with their list prices where the list price is at leastdouble

the minimum price. Thereport should start with the product name having the maximum list pricesatisfying

this condition.

Evaluate the followingSQL statement:

  SQL>SELECTprod_name,prod_list_price
FROM products

WHERE prod_list_price>= 2 * prod_min_price

Which ORDER BY clausescan be added to the above SQL statement to get the correct output?

  (Choose all that apply.)
DSC00013.jpg
A. ORDER BYprod_list_price DESC, prod_name;

B. ORDER BY(2*prod_min_price)DESC, prod_name;

C. ORDER BY prod_name,(2*prod_min_price)DESC;

D. ORDER BY prod_nameDESC, prod_list_price DESC;

E. ORDER BYprod_list_price DESC, prod_name DESC;

  Answer: AE
  解析:
  这道题跟前面的一道题一样,题意要求prod_list_price降序排列,并且优先对prod_list_price排序
  所以选项为A E

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