W3. SQL Aggregate Functions

Question 1

Q: What is an SQL Aggregate function?

Answer 1

A: A function that performs a calculation on a set of values and returns a single result.

Question 2

Q: In SQL, with which clause are aggregate functions commonly used?

Answer 2

A: The GROUP BY clause.

Question 3

Q: What does the GROUP BY clause do in SQL?

Answer 3

A: It splits the result set into groups, allowing aggregate functions to return a single value for each group.

Question 4

Q: Name some commonly used SQL aggregate functions.

Answer 4

MIN() - smallest value
MAX() - largest value
COUNT() - number of rows
SUM() - total sum of a column
AVG() - average of a column

Question 5

Q: What does the MIN() function do?

Answer 5

A: Returns the smallest value in a selected column.

Question 6

Q: What does the MAX() function do?

Answer 6

A: Returns the largest value in a selected column.

Question 7

Q: What does the COUNT() function do?

Answer 7

A: Returns the number of rows in a set, including NULL values.

Question 8

Q: What does the SUM() function do?

Answer 8

A: Returns the total sum of a numerical column.

Question 9

Q: What does the AVG() function do?

Answer 9

A: Returns the average value of a numerical column.

Question 10

Q: Do aggregate functions ignore NULL values?

Answer 10

A: Yes, except for COUNT().