Oracle Database 12c SQL OCA/OCP 1Z0-071题库(31-35题)

QUESTION 31

Which three statements are true regarding subqueries? (Choose three.)

A. Multiple columns or expressions can be compared between the main query and subquery.

B. Subqueries can contain ORDER BY but not the GROUP BY clause.

C. Main query and subquery can get data from different tables.

D. Subqueries can contain GROUP BY and ORDER BY clauses.

E. Main query and subquery must get data from the same tables.

F. Only one column or expression can be compared between the main query and subquery.

答案：ACD

解析：父查询和子查询可以查询不同的表，其他参见24题解析。

QUESTION 32

Which statement is true regarding the default behavior of the ORDER BY clause?

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

B. NULL values are not considered at all by the sort operation.

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

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

答案：A

解析：ORDER BY：排序大小写敏感，大写小于小写；NULL大于一切值；ORDER BY的列或表达式可以不是SELECT选择的列；默认升序。（可参见21题）

QUESTION 33

Examine the structure of the MEMBERS table.

Name                          NULL?                 Type
------------------              --------------         ----------------
MEMBER                     NOT NULL           VARCHAR2(6)
FIRST_NAME                                           VARCHAR2(50)
LAST_NAME                NOT NULL           VARCHAR2(50)
ADDREDD                                               VARCHAR2(50)          
CITY                                                        VARCHAR2(25)      
STATE                          NOT NULL         VARCHAR2(3)

Which query can be used to display the last names and city names only for members from the states MO and MI?

A. SELECT last_name, city FROM members WHERE state ='MO' AND state ='MI';

B. SELECT last_name, city FROM members WHERE state LIKE 'M%';

C. SELECT last_name, city FROM members WHERE state IN ('MO', 'MI');

D. SELECT DISTINCT last_name, city FROM members WHERE state ='MO' OR state ='MI';

答案：C

QUESTION 34

Which statement is true about an inner join specified in a query’s WHERE clause?

A. It only applies for equijoin conditions.

B. It applies for equijoin and nonequijoin conditions.

C. It requires column names to be the same in all tables being joined.

D. It must have primary-key and foreign-key constraints defined on the join columns.

答案：B

QUESTION 35

Which task can be performed by using a single Data Manipulation Language (DML) statement?

A. adding a column constraint while inserting a row into a table

B. adding a column with a default value while inserting a row into a table

C. removing all data only from a single column on which a unique constraint is defined

D. removing all data only from a single column on which a primary key constraint is defined

答案：C

解析：UNIQUE对删除数据无限制。

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