Oracle Database Programming with SQL Section 7
1. The AVG, SUM, VARIANCE, and STDDEV functions can be used with which of the following?
♦All except numeric
♦Only numeric data types (*)
♦Integers only
♦Any data type
2. Which aggregate function can be used on a column of the DATE data type?
♦MAX (*)
♦STDDEV
♦AVG
♦SUM
3. The VENDORS table contains these columns:
VENDOR_ID NUMBER Primary Key
NAME VARCHAR2(30)
LOCATION_ID NUMBER
ORDER_DT DATE
ORDER_AMOUNT NUMBER(8,2)
Which two clauses represent valid uses of aggregate functions for this table?
(Choose all correct answers)
♦SELECT SUM(order_dt)
♦FROM MAX(order_dt)
♦SELECT SUM(order_amount) (*)
♦WHERE MAX(order_dt) = order_dt
♦SELECT MIN(AVG(order_amount)) (*)
4. Group functions return a value for ________________ and ________________ null values in their computations.
♦a row set, ignore (*)
♦each row, include
♦each row, ignore
♦a row set, include
5. Which group function would you use to display the lowest value in the SALES_AMOUNT column?
♦COUNT
♦MAX
♦AVG
♦MIN (*)
6. Given the following data in the employees table (employee_id, salary, commission_pct)
DATA: (143, 2600, null
144, 2500, null
149, 10500, .2
174, 11000, .3
176, 8600, .2
178, 7000, .15)
What is the result of the following statement:
SELECT SUM(commission_pct), COUNT(salary)
FROM employees
WHERE employee_id IN( 143,144,149,174,176,178);
♦SUM = 1.85 and COUNT =4
♦SUM = 1.85 and COUNT = 6
♦SUM = .85 and COUNT = 4
♦SUM = .85 and COUNT = 6 (*)
7. The TRUCKS table contains these columns:
TRUCKS:
TYPE VARCHAR2(30)
YEAR DATE
MODEL VARCHAR2(20)
PRICE NUMBER(10)
Which SELECT statement will return the average price for the 4×4 model?
♦SELECT AVG(price), model
FROM trucks
WHERE model IS ‘4×4’;
♦SELECT AVG(price)
FROM trucks
WHERE model IS 4×4;
♦SELECT AVG(price)
FROM trucks
WHERE model IS ‘4×4’;
♦SELECT AVG(price)
FROM trucks
WHERE model = ‘4×4’;
(*)
8. You need to compute the total salary amount for all employees in department 10. Which group function will you use?
♦COUNT
♦SUM (*)
♦VARIANCE
♦MAX
9. Evaluate this SELECT statement:
SELECT COUNT(*)
FROM products;
Which statement is true?
♦The number of rows in the table is displayed. (*)
♦An error occurs due to an error in the SELECT clause.
♦An error occurs because no WHERE clause is included in the SELECT statement.
♦The number of unique PRODUCT_IDs in the table is displayed.
10. The EMPLOYEES table contains these columns:
EMPLOYEE_ID NUMBER(9)
LAST_NAME VARCHAR2(20)
FIRST_NAME VARCHAR2(20)
SALARY NUMBER(7,2)
DEPARTMENT_ID NUMBER(9)
You need to display the number of employees whose salary is greater than $50,000? Which SELECT would you use?
♦SELECT COUNT(*)
FROM employees
WHERE salary < 50000;
♦SELECT * FROM employees
WHERE salary < 50000; ♦SELECT COUNT(*) FROM employees WHERE salary > 50000
GROUP BY employee_id, last_name, first_name, salary, department_id;
♦SELECT COUNT(*)
FROM employees
WHERE salary > 50000;
(*)
♦SELECT * FROM employees
WHERE salary > 50000;
11. Evaluate this SQL statement:
SELECT COUNT (amount)
FROM inventory;
What will occur when the statement is issued?
♦The statement will count the number of rows in the INVENTORY table where the AMOUNT column is not null. (*)
♦The statement will return the total number of rows in the AMOUNT column.
♦The statement will replace all NULL values that exist in the AMOUNT column.
♦The statement will return the greatest value in the INVENTORY table.
12. To include null values in the calculations of a group function, you must:
♦Group functions can never use null values
♦Convert the null to a value using the NVL( ) function (*)
♦Count the number of null values in that column using COUNT
♦Precede the group function name with NULL
13. Which statement about the COUNT function is true?
♦The COUNT function always ignores null values by default. (*)
♦The COUNT function can be used to determine the number of unique, non-null values in a column.
♦The COUNT function can be used to find the maximum value in each column.
♦The COUNT function ignores duplicates by default.
14. Which SELECT statement will calculate the number of rows in the PRODUCTS table?
♦SELECT ROWCOUNT FROM products;
♦SELECT COUNT(products);
♦SELECT COUNT (*) FROM products; (*)
♦SELECT COUNT FROM products;
15. Using your existing knowledge of the employees table, would the following two statements produce the same result?
SELECT COUNT(*)
FROM employees;
SELECT COUNT(commission_pct)
FROM employees;
♦The second statement is invalid
♦The first statement is invalid
♦Yes
♦No (*)
16. The TRUCKS table contains these columns:
TRUCKS:
TYPE VARCHAR2(30)
YEAR DATE
MODEL VARCHAR2(20)
PRICE NUMBER(10)
Which SELECT statement will return the average price for the 4×4 model?
♦SELECT AVG(price), model
FROM trucks
WHERE model IS ‘4×4’;
♦SELECT AVG(price)
FROM trucks
WHERE model IS 4×4;
♦SELECT AVG(price)
FROM trucks
WHERE model IS ‘4×4’;
♦SELECT AVG(price)
FROM trucks
WHERE model = ‘4×4’;
(*)
17. Which group function would you use to display the highest salary value in the EMPLOYEES table?
♦MIN
♦MAX (*)
♦AVG
♦COUNT
18. You need to compute the total salary amount for all employees in department 10. Which group function will you use?
♦SUM (*)
♦MAX
♦VARIANCE
♦COUNT
19. You need to calculate the average salary of employees in each department. Which group function will you use?
♦AVG (*)
♦AVERAGE
♦MEDIAN
♦MEAN
20. Examine the data in the PAYMENT table:
PAYMENT_ID CUSTOMER_ID PAYMENT_DATE PAYMENT_TYPE PAYMENT_AMOUNT
86590586 8908090 10-Jun-2003 BASIC 859.00
89453485 8549038 15-Feb-2003 INTEREST 596.00
85490345 5489304 20-Mar-2003 BASIC 568.00
You need to determine the average payment amount made by each customer in January, February, and March of 2003.
Which SELECT statement should you use?
♦SELECT AVG(payment_amount)
FROM payment
WHERE payment_date
BETWEEN ’01-Jan-2003′ AND ’31-Mar-2003′;
(*)
♦SELECT AVG(payment_amount)
FROM payment;
♦SELECT AVG(payment_amount)
FROM payment
WHERE TO_CHAR(payment_date) IN (Jan, Feb, Mar);
♦SELECT SUM(payment_amount)
FROM payment
WHERE payment_date BETWEEN ’01-Jan-2003′ and ’31-Mar-2003′;
21. Which group function would you use to display the lowest value in the SALES_AMOUNT column?
♦MIN (*)
♦MAX
♦COUNT
♦AVG
22. The AVG, SUM, VARIANCE, and STDDEV functions can be used with which of the following?
♦Integers only
♦Only numeric data types (*)
♦Any data type
♦All except numeric
23. Which group function would you use to display the total of all salary values in the EMPLOYEES table?
♦COUNT
♦MAX
♦AVG
♦SUM (*)
24. Evaluate this SELECT statement:
SELECT COUNT(*)
FROM products;
Which statement is true?
♦The number of unique PRODUCT_IDs in the table is displayed.
♦An error occurs due to an error in the SELECT clause.
♦The number of rows in the table is displayed. (*)
♦An error occurs because no WHERE clause is included in the SELECT statement.
25. Evaluate this SQL statement:
SELECT COUNT (amount)
FROM inventory;
What will occur when the statement is issued?
♦The statement will return the greatest value in the INVENTORY table.
♦The statement will replace all NULL values that exist in the AMOUNT column.
♦The statement will return the total number of rows in the AMOUNT column.
♦The statement will count the number of rows in the INVENTORY table where the ♦AMOUNT column is not null. (*)
26. Group functions can avoid computations involving duplicate values by including which keyword?
♦DISTINCT (*)
♦SELECT
♦UNLIKE
♦NULL
27. The EMPLOYEES table contains these columns:
EMPLOYEE_ID NUMBER(9)
LAST_NAME VARCHAR2(20)
FIRST_NAME VARCHAR2(20)
SALARY NUMBER(7,2)
DEPARTMENT_ID NUMBER(9)
You need to display the number of employees whose salary is greater than $50,000? Which SELECT would you use?
♦SELECT * FROM employees
WHERE salary > 50000;
♦SELECT COUNT(*)
FROM employees
WHERE salary > 50000;
(*)
♦SELECT * FROM employees
WHERE salary < 50000; ♦SELECT COUNT(*) FROM employees WHERE salary > 50000
GROUP BY employee_id, last_name, first_name, salary, department_id;
♦SELECT COUNT(*)
FROM employees
WHERE salary < 50000;
28. Which statement about the COUNT function is true?
♦The COUNT function always ignores null values by default. (*)
♦The COUNT function can be used to find the maximum value in each column.
♦The COUNT function ignores duplicates by default.
♦The COUNT function can be used to determine the number of unique, non-null values in a column.
29. Which SELECT statement will calculate the number of rows in the PRODUCTS table?
♦SELECT COUNT FROM products;
♦SELECT ROWCOUNT FROM products;
♦SELECT COUNT (*) FROM products; (*)
♦SELECT COUNT(products);
30. The STYLES table contains this data:
STYLE_ID STYLE_NAME CATEGORY COST
895840 SANDAL 85940 12.00
968950 SANDAL 85909 10.00
869506 SANDAL 89690 15.00
809090 LOAFER 89098 10.00
890890 LOAFER 89789 14.00
857689 HEEL 85940 11.00
758960 SANDAL 86979
You issue this SELECT statement:
SELECT COUNT(category)
FROM styles;
Which value is displayed?
♦7 (*)
♦6
♦The statement will NOT execute successfully.
♦0
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