You need to change the definition of a...

单项选择题You need to change the definition of an existing table. The COMMERCIALS table needs its DESCRIPTION column changed to hold varying length characters up to 2000 bytes. The column can currently hold 1000 bytes per value. The table contains 20000 rows.Which statement is valid?（）

A. ALTER TABLE commercials MODIFY (description CHAR2(2000));
B. ALTER TABLE commercials CHANGE (description CHAR2(2000));
C. ALTER TABLE commercials CHANGE (description VARCHAR2 (2000));
D. ALTER TABLE commercials MODIFY (description VARCHAR2 (2000));
E. You cannot increase the size of a column if the table has rows.

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1.单项选择题In which case would you use a FULL OUTER JOIN?（）

A. Both tables have NULL values.
B. You want all unmatched data from one table.
C. You want all matched data from both tables.
D. You want all unmatched data from both tables.
E. One of the tables has more data than the other.
F. You want all matched and unmatched data from only one table.

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2.单项选择题 You added a PHONE_NUMBER column of NUMBER data type to an existing EMPLOYEES table. The EMPLOYEES table already contains records of 100 employees. Now, you want to enter the phone numbers of each of the 100 employees into the table. Some of the employees may not have a phone number available.
Which data manipulation operation do you perform?（）

A. MERGE
B. INSERT
C. UPDATE
D. ADD
E. ENTER
F. You cannot enter the phone numbers for the existing employee records.

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3.单项选择题What does the TRUNCATE statement do?（）

A. Removes the table
B. Removes all rows from a table
C. Shortens the table to 10 rows
D. Removes all columns from a table
E. Removes foreign keys from a table

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4.单项选择题Which is an /SQL*Plus command?（）

A. INSERT
B. UPDATE
C. SELECT
D. DESCRIBE
E. DELETE
F. RENAME

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5.单项选择题 Examine the data of the EMPLOYEES table.
EMPLOYEES (EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID)

Evaluate this SQL statement:

What is its output?（）

A.
B.
C.
D.
E. The SQL statement produces an error.

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6.单项选择题Which SELECT statement should you use to extract the year from the system date and display it in the format "1998"?（）

A. SELECT TO_CHAR(SYSDATE,'yyyy') FROM dual;
B. SELECT TO_DATE(SYSDATE,'yyyy') FROM dual;
C. SELECT DECODE(SUBSTR(SYSDATE, 8), 'YYYY') FROM dual;
D. SELECT DECODE(SUBSTR(SYSDATE, 8), 'year') FROM dual;
E. SELECT TO_CHAR(SUBSTR(SYSDATE, 8,2),'yyyy') FROM dual;

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7.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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8.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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9.单项选择题Which clause should you use to exclude group results?（）

A. WHERE
B. HAVING
C. RESTRICT
D. GROUP BY
E. ORDER BY

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10.单项选择题 Scott issues the SQL statements:
CREATE TABLE dept
(deptno NUMBER(2),
dname VARCHAR2(14),
loc VARCHAR2(13)};
GRANT SELECT
ON DEPT
T0 SUE;
If Sue needs to select from Scott's DEPT table, which command should she use?（）

A.SELECT*FROMDEPT；
B.SELECT*FROMSCOTT.DEPT；
C.SELECT*FROMDBASCOTTDEPT；
D.SELECT*FROMALL_USERSWHEREUSER_NAME='；SCOTT'；ANDTABLENAME='；DEPT'；；

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