AVG function in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the AVG function do in SQL?

The AVG function calculates the average (mean) value of a numeric column in a table.

beginner

How do you use the AVG function to find the average price from a products table?

Use: SELECT AVG(price) FROM products; This returns the average of all values in the price column.

beginner

Can the AVG function be used with non-numeric columns?

No, AVG only works with numeric columns like integers or decimals. Using it on text columns will cause an error.

intermediate

What happens if the AVG function is used on a column with NULL values?

NULL values are ignored by AVG. It calculates the average only from non-NULL values.

intermediate

How can you find the average salary per department using AVG?

Use GROUP BY: SELECT department, AVG(salary) FROM employees GROUP BY department; This shows average salary for each department.

What does the SQL AVG function return?

A The average value of a numeric column

B The total sum of a numeric column

C The highest value in a column

D The number of rows in a table

AVG calculates the mean (average) of numeric values in a column.

Which SQL query correctly finds the average age from a table named users?

A SELECT AVG(age) FROM users;

B SELECT SUM(age) FROM users;

C SELECT COUNT(age) FROM users;

D SELECT MAX(age) FROM users;

AVG(age) returns the average age; SUM, COUNT, and MAX do different calculations.

How does AVG handle NULL values in a column?

A It causes an error

B It treats NULL as zero

C It ignores NULL values

D It counts NULL as one

AVG skips NULLs and calculates average only from existing numeric values.

Can AVG be used on a text column?

A Yes, but only if text is numeric strings

B No, AVG only works on numeric columns

C Yes, AVG works on any column

D Only if text is converted first

AVG requires numeric data types; text columns cause errors.

Which SQL clause is used with AVG to get averages per group?

A HAVING

B ORDER BY

C WHERE

D GROUP BY

GROUP BY groups rows so AVG can calculate averages for each group.

Explain how the AVG function works and how it treats NULL values.

Think about how you find an average in real life and what happens if some data is missing.

Describe how to use AVG with GROUP BY to find averages per category.

Imagine you want average scores per class in a school.