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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1.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

2.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

3.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.

5.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.

6.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.

7.多项选择题Which two are character manipulation functions? ()

A. TRIM
B. REPLACE
C. TRUNC
D. TO_DATE
E. MOD
F. CASE

8.单项选择题Evaluate this SQL statement: SELECT e.EMPLOYEE_ID,e.LAST_NAME,e.DEPARTMENT_ID, d.DEPARTMENT_NAME FROM EMP e, DEPARTMENT 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

9.单项选择题You need to perform certain data manipulation operations through a view called EMP_DEPT_VU, which you previously created. You want to look at the definition of the view (the SELECT statement on which the view was create.) How do you obtain the definition of the view? ()

A. Use the DESCRIBE command in the EMP_DEPT VU view.
B. Use the DEFINE VIEW command on the EMP_DEPT VU view.
C. Use the DESCRIBE VIEW command on the EMP_DEPT VU view.
D. Query the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view.
E. Query the USER_SOURCE data dictionary view to search for the EMP_DEPT_VU view.
F. Query the USER_OBJECTS data dictionary view to search for the EMP_DEPT_VU view.

10.单项选择题You need to display the last names of those employees who have the letter "A" as the second character in their names. Which SQL statement displays the required results? ()

A. SELECT last_name FROM EMP WHERE last_ name LIKE '_A%';
B. SELECT last_name FROM EMP WHERE last name ='*A%'
C. SELECT last_name FROM EMP WHERE last name ='_A%';
D. SELECT last_name FROM EMP WHERE last name LIKE '*A%'