Which SELECT statement should you use ...

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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1.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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2.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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3.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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4.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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5.单项选择题What is true about joining tables through an equijoin?（）

A. You can join a maximum of two tables through an equijoin.
B. You can join a maximum of two columns through an equijoin.
C. You specify an equijoin condition in the SELECT or FROM clauses of a SELECT statement.
D. To join two tables through an equijoin, the columns in the join condition must be primary key and foreign key columns.
E. You can join n tables (all having single column primary keys) in a SQL statement by specifying a minimum of n-1 join conditions.

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6.多项选择题Which two statements about subqueries are true?（）

A. A single row subquery can retrieve data from only one table.
B. A SQL query statement cannot display data from table B that is referred to in its subquery, unless table B is included in the main query's FROM clause.
C. A SQL query statement can display data from table B that is referred to in its subquery, without including table B in its own FROM clause.
D. A single row subquery can retrieve data from more than one table.
E. A single row subquery cannot be used in a condition where the LIKE operator is used for comparison.
F. A multiple-row subquery cannot be used in a condition where the LIKE operator is used for comparison.

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7.单项选择题You need to calculate the total of all salaries in the accounting department. Which group function should you use?（）

A. MAX
B. MIN
C. SUM
D. COUNT
E. TOTAL
F. LARGEST

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8.单项选择题 Examine the data in the EMPLOYEES and EMP_HIST tables:

The EMP_HIST table is updated at the end of every year. The employee ID, name, job ID, and salary of each existing employee are modified with the latest data. New employee details are added to the table.
Which statement accomplishes this task?（）

A.
B.
C.
D.

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9.单项选择题You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=".What happens when the main query is executed?（）

A. The main query executes with the first value returned by the subquery.
B. The main query executes with the last value returned by the subquery.
C. The main query executes with all the values returned by the subquery.
D. The main query fails because the multiple-row subquery cannot be used with the comparison operator.
E. You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

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10.多项选择题Which three statements correctly describe the functions and use of constraints? （）

A.Constraints provide data independence.
B.Constraints make complex queries easy.
C.Constraints enforce rules at the view level.
D.Constraints enforce rules at the table level.
E.Constraints prevent the deletion of a table if there are dependencies.
F.Constraints prevent the deletion of an index if there are dependencies.

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