SQL Finals

What does the COUNT(*) function do?

• Adds values

• Finds the average

• Counts all rows

• Deletes rows

Which query returns the total number of students in the students table?

• SELECT SUM(*) FROM students;

• SELECT COUNT(*) FROM students;

• SELECT AVG(*) FROM students;

How do you get the average score from a column named grade from students table?

___________

Which aggregate function is used to add values in a column?

____

Find the total salary of all employees. Table name employees

What’s wrong with this query?

SELECT COUNT(name), age FROM students;

• Nothing

• Missing GROUP BY

• Should use SUM

You want the number of students older than 18. Which is correct?

• SELECT COUNT(age > 18) FROM students;

• SELECT COUNT(*) FROM students WHERE age > 18;

• SELECT SUM(age > 18) FROM students;

The AVG() function can be used on text columns.

• True

• False

SUM() and AVG() ignore NULL values.

• True

• False

This query is valid:

SELECT COUNT(*), SUM(salary), AVG(salary) FROM employees;

• No

• Yes