SQL Multiple Aggregates

List several aggregate functions in the same SELECT — each one is computed independently, over the same groups, in a single pass.

What & Why

Nothing stops a query from computing several different summaries at once — COUNT, SUM, AVG, MIN, and MAX can all appear side by side in the same SELECT list. Postgres computes each one independently, but all of them share the exact same groups formed by GROUP BY — so there's no cost to asking for four summaries instead of one; it's still a single pass over the data.

See How It Works

BUSINESS QUESTION

Marketing wants campaign count, total spend, and average spend together.

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

EXAMPLE QUERY

SELECT
  channel,
  COUNT(*) AS campaigns,
  SUM(spend) AS total_spend,
  ROUND(AVG(spend), 2) AS avg_spend
FROM marketing.campaigns
GROUP BY channel
ORDER BY total_spend DESC, channel;

RESULT — exact output from the displayed Queryflo rows

channel	campaigns	total_spend	avg_spend
google_ads	2	115000.00	57500.00
linkedin	1	50000.00	50000.00
email	1	45000.00	45000.00

Every result row summarizes one real campaign channel.

Now You Try

Practice this concept

Marketing wants campaign count, total spend, and average spend together.

Available schema

marketing

Prefix tables with marketing.table_name.

channelcampaignstotal_spendavg_spend

marketing.campaigns

Column	Type
id	integer
name	text
channel	text
spend	numeric
start_date	date
end_date	date
status	text
target_segment	text
legacy_id	text

query.sql

Intermediate business practice