A subquery can be used to（）.

单项选择题A subquery can be used to（）.

A.create groups of data
B.sort data in a specific order
C.convert data to a different format
D.retrieve data based on an unknown condition

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你可能感兴趣的试题

1.单项选择题Mary has a view called EMP_DEPT_LOC_VU that was created based on the EMPLOYEES, DEPARTMENTS, and LOCATIONS tables. She granted SELECT privilege to Scott on this view. Which option enables Scott to eliminate the need to qualify the view with the name MARY.EMP_DEPT_LOC_VU each time the view is referenced?（）

A.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE PRIVATE SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
B.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
C.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE LOCAL SYNONYM EDL_VU FOR mary.EMP_DEPT_LOC_VU; then he can prefix the columns with this synonym.
D.Scott can create a synonym for the EMP_DEPT_LOC_VU by using the command CREATE SYNONYM EDL_VU ON mary(EMP_DEPT_LOC_VU); then he can prefix the columns with this synonym.
E.Scott cannot create a synonym because synonyms can be created only for tables.
F.Scott cannot create any synonym for Mary's view. Mary should create a private synonym for the view and grant SELECT privilege on that synonym to Scott.

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2.单项选择题 The EMP table contains these columns:
EMPLOYEE_ID NUMBER(4)
EMPNAME VARCHAR2 (25)
SALARY NUMBER(9,2)
HIRE_DATE DATE
You query the database with this SQL statement:
SELECT empname,hire_date HIREDATE, salary
FROM EMP
ORDER BY hire_date;
How will the results be sorted?（）

A.randomly
B.ascending by date
C.descending by date
D.ascending alphabetically
E.descending alphabetically

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3.多项选择题Evaluate the SQL statement: TRUNCATE TABLE DEPT;Which three are true about the SQL statement? （）

A.It releases the storage space used by the table.
B.It does not release the storage space used by the table.
C.You can roll back the deletion of rows after the statement executes.
D.You can NOT roll back the deletion of rows after the statement executes.
E.An attempt to use DESCRIBE on the DEPT table after the TRUNCATE statement executes will display an error.
F.You must be the owner of the table or have DELETE ANY TABLE system privileges to truncate the DEPT table.

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4.单项选择题 The EMPLOYEES table contains these columns: LAST_NAME VARCHAR2 (25)
SALARY NUMBER (6,2)
COMMISSION_PCT NUMBER (6)
You need to write a query that will produce these results:
1.Display the salary multiplied by the commission_pct.
2.Exclude employees with a zero commission_pct.
3.Display a zero for employees with a null commission value.
Evaluate the SQL statement:
SELECT LAST_NAME, SALARY*COMMISSION_PCT
FROM EMPLOYEES
WHERE COMMISSION_PCT IS NOT NULL;
What does the statement provide?（）

A.all of the desired results
B.two of the desired results
C.one of the desired results
D.an error statement

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5.多项选择题Which three are DATETIME data types that can be used when specifying column definitions? （）

A.TIMESTAMP
B.INTERVAL MONTH TO DAY
C.INTERVAL DAY TO SECOND
D.INTERVAL YEAR TO MONTH
E.TIMESTAMP WITH DATABASE TIMEZONE

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6.单项选择题You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty. Which statement accomplishes this task?（）

A.ALTER TABLE students ADD PRIMARY KEY student_id;
B.ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student_id);
C.ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY student_id;
D.ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
E.ALTER TABLE students MODIFY CONSTRAINT stud_id_pk PRIMARY KEY (student_id);

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7.多项选择题 Click the Exhibit button and examine the data from the EMP table.
The COMMISSION column shows the monthly commission earned by the employee.
Which three tasks would require subqueries or joins in order to be performed in a single step?（）

A.deleting the records of employees who do not earn commission
B.increasing the commission of employee 3 by the average commission earned in department 20
C.finding the number of employees who do NOT earn commission and are working for department 20
D.inserting into the table a new employee 10 who works for department 20 and earns a commission that is equal to the commission earned by employee 3
E.creating a table called COMMISSION that has the same structure and data as the columns EMP_ID and COMMISSION of the EMP table
F.decreasing the commission by 150 for the employees who are working in department 30 and earning a commission of more than 800

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8.单项选择题 Evaluate this SQL statement:
SELECT e.EMPLOYEE_ID,e.LAST_NAME,e.DEPARTMENT_ID, d.DEPARTMENT_NAME
FROM EMPLOYEES e, DEPARTMENTS d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID;
In the statement, which capabilities of a SELECT statement are performed?（）

A.selection, projection, join
B.difference, projection, join
C.selection, intersection, join
D.intersection, projection, join
E.difference, projection, product

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9.单项选择题 Click the Exhibit button and examine the data from the ORDERS and CUSTOMERS tables.
Evaluate this SQL statement:
SELECT cust_id, ord_total
FROM orders
WHERE ord_total > ANY(SELECT ord_total
FROM orders
WHERE cust_id IN (SELECT cust_id
FROM customers WHERE city LIKE'New York'));
What is the result when the above query is executed?（）

A.A
B.B
C.C
D.D
E.E

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10.单项选择题 Examine the structure of the EMP_DEPT_VU view:
Column Name Type Remarks
EMPLOYEE_ID NUMBER From the EMPLOYEES table
EMP_NAME VARCHAR2(30) From the EMPLOYEES table
JOB_ID VARCHAR2(20) From the EMPLOYEES table
SALARY NUMBER From the EMPLOYEES table
DEPARTMENT_ID NUMBER From the DEPARTMENTS table
DEPT_NAME VARCHAR2(30) From the DEPARTMENTS table
Which SQL statement produces an error?（）

A.SELECT*FROMemp_dept_vu；
B.SELECTdepartment_id，SUM（salary）FROMemp_dept_vuGROUPBYdepartment_id；
C.SELECTdepartment_id，job_id，AVG（salary）FROMemp_dept_vuGROUPBYdepartment_id，job_id；
D.SELECTjob_id，SUM（salary）FROMemp_dept_vuWHEREdepartment_idIN（10，20）GROUPBYjob_idHAVINGSUM（salary）>；20000；
E.Noneofthestatementsproduceanerror；allarevalid

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