AVG function in SQL - 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 salary from an Employees table?

Use: <br>SELECT AVG(salary) FROM Employees;<br>This returns the average salary of all employees.

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 or dates 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 the non-NULL values.

intermediate

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

Use GROUP BY with AVG:<br>SELECT department, AVG(salary) FROM Employees GROUP BY department;<br>This shows average salary for each department.

What does the SQL AVG function calculate?

A The total sum of a numeric column

B The average value of a numeric column

C The maximum value in a column

D The number of rows in a table

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

Which SQL query correctly finds the average price from a Products table?

A SELECT AVG(price) FROM Products;

B SELECT SUM(price) FROM Products;

C SELECT COUNT(price) FROM Products;

D SELECT MAX(price) FROM Products;

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

How does AVG handle NULL values in a column?

A It counts NULL as one

B It treats NULL as zero

C It ignores NULL values and averages only non-NULL values

D It returns NULL if any NULL exists

AVG skips NULLs and calculates average from existing numeric values.

Can AVG be used on a text column?

A No, AVG only works with numeric columns

B Yes, AVG converts text to numbers automatically

C Yes, AVG counts the number of text entries

D No, AVG only works with date columns

AVG requires numeric data; text columns cause errors.

How do you find the average salary per department?

A SELECT department, SUM(salary) FROM Employees;

B SELECT AVG(salary) FROM Employees;

C SELECT department FROM Employees WHERE AVG(salary);

D SELECT department, AVG(salary) FROM Employees GROUP BY department;

GROUP BY groups rows by department, AVG calculates average salary per group.

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

Think about how average is calculated in math and what happens if some values are missing.

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

Grouping data helps calculate averages for each group separately.