Aggregation Functions — Learn free

Self-check

Questions 1–10 of 10

1. What do aggregation functions do?
Question 1A. Encrypt values in a columnB. Perform calculations on a set of values to return a single summarised resultC. Split a table into multiple tablesD. Rename columns in a result setE. Convert data types between text and numbers
2. Instead of listing every employee's salary, what might an aggregation function be used to obtain?
Question 2A. Each employee's job titleB. The list of departments sorted alphabeticallyC. The total salary expenditure for a departmentD. The employee with the most recent start dateE. The number of columns in the employees table
3. Which SQL aggregation function counts the number of rows in a result set?
Question 3A. SUMB. AVGC. MAXD. COUNTE. DISTINCT
4. Which SQL function computes the mean of values in a numeric column?
Question 4A. SUMB. MINC. COUNTD. HAVINGE. AVG
5. What does the SQL GROUP BY clause do?
Question 5A. Groups rows based on the values in one or more columns and applies aggregation functions to each groupB. Removes duplicate values from the result setC. Sorts the result set in ascending orderD. Filters rows before aggregationE. Joins two tables on a common column
6. What is the role of HAVING in a SQL query?
Question 6A. It selects the maximum value in a columnB. It filters the results of a GROUP BY based on a specified conditionC. It counts the rows in each groupD. It removes duplicate rowsE. It defines which table to query
7. What does SELECT DISTINCT department FROM employees; return?
Question 7A. The number of employees in each departmentB. The highest-paid departmentC. The unique department values with duplicates removedD. All departments including duplicatesE. The average salary per department
8. Which query returns the lowest salary in the employees table?
Question 8A. SELECT MAX(salary) AS LowestSalary FROM employees;B. SELECT AVG(salary) AS LowestSalary FROM employees;C. SELECT COUNT(salary) AS LowestSalary FROM employees;D. SELECT MIN(salary) AS LowestSalary FROM employees;E. SELECT SUM(salary) AS LowestSalary FROM employees;
9. What is described as the ultimate purpose of using aggregation functions?
Question 9A. To increase the number of rows in a tableB. To enforce referential integrityC. To back up the databaseD. To speed up insertsE. To extract valuable insights from data by summarising it into a more manageable and interpretable view
10. Which of the following is NOT one of the common SQL aggregation-related functions and clauses listed?
Question 10A. MEDIANB. SUMC. COUNTD. GROUP BYE. HAVING