SQL SUM and AVG Functions

What are SUM and AVG?

SUM adds up all values in a column. AVG calculates the arithmetic mean. Both ignore NULL values.

Syntax

SELECT SUM(column) FROM table_name;
SELECT AVG(column) FROM table_name;

When to Use

• Calculating total revenue, hours, or quantity
• Finding average price, age, or score
• Creating summary reports with GROUP BY

Key Points

1. Numeric Columns Only — SUM and AVG work on numeric data types.
2. NULLs Ignored — Both functions skip NULL values. This affects the average.
3. Rounding — Use ROUND(AVG(column), 2) to limit decimal places.
4. With GROUP BY — Segment totals and averages by category.
5. DISTINCT — SUM(DISTINCT column) and AVG(DISTINCT column) only consider unique values.