SQL AVG

The sum divided by the count — but the count only includes non-NULL rows, which matters more than it sounds.

What & Why

AVG(column) computes the mean — sum divided by count. Critically, both the sum and the count ignore NULL values entirely, which is covered in depth in the final lesson of this series.

See How It Works

BUSINESS QUESTION

Average spend across the campaign portfolio.

id	name	channel	spend	start_date	end_date	status	target_segment
1	Spring Launch	google_ads	55000.00	2024-01-15	2024-03-31	active	smb
2	Retention Webinar	email	45000.00	2024-02-10	2024-04-15	active	enterprise
3	Finance Retargeting	linkedin	50000.00	2024-03-12	2024-05-31	active	enterprise
4	Enterprise Search	google_ads	60000.00	2024-04-01	2024-06-30	active	enterprise

Watch AVG divide the sum by the countStep 1 of 2

SUM(spend) = 55,000 + 45,000 + 50,000 + 60,000

id	campaign	spend	sum contribution
1	Spring Launch	55,000.00	+ 55,000.00
2	Retention Webinar	45,000.00	+ 45,000.00
3	Finance Retargeting	50,000.00	+ 50,000.00
4	Enterprise Search	60,000.00	+ 60,000.00

SUM(spend)210,000

First, AVG adds the four non-NULL spend values.

EXAMPLE QUERY

SELECT AVG(spend) AS avg_spend
FROM marketing.campaigns;

Now You Try

Practice this concept

Marketing wants average lead score by source.

Available schema

marketing

Prefix tables with marketing.table_name.

sourceavg_lead_score

marketing.leads

Column	Type
id	integer
campaign_id	integer
email	text
created_at	timestamp with time zone
qualified_at	timestamp with time zone
converted_at	timestamp with time zone
lead_score	integer
source	text
country	text
archive_status	text

query.sql

Beginner business practice