SQL JOIN Using ON

The ON keyword explicitly states the join condition — the modern, standard, and clearest way to write any join.

What & Why

Every join example so far has used ON to state the matching condition directly, right where the join is written: JOIN table2 ON table1.col = table2.col. This keeps the join logic and the join itself together in one place.

See How It Works

BUSINESS QUESTION

Marketing attaches each lead to its campaign through the declared campaign foreign key.

id	campaign_id	email	created_at	qualified_at	converted_at	lead_score	source	country
301	1	ana@example.com	2024-01-21 09:10:00+00	2024-01-22 11:00:00+00	2024-02-02 10:00:00+00	86	google_ads	US
302	1	ben@example.com	2024-01-24 12:40:00+00	NULL	NULL	52	google_ads	CA
303	2	chloe@example.com	2024-02-16 08:30:00+00	2024-02-18 14:20:00+00	NULL	74	email	GB
304	3	dev@example.com	2024-03-20 17:15:00+00	2024-03-21 09:00:00+00	2024-04-04 16:00:00+00	91	linkedin	US

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
  l.id AS lead_id,
  c.name AS campaign_name,
  l.source
FROM marketing.leads l
JOIN marketing.campaigns c
  ON c.id = l.campaign_id
ORDER BY lead_id;

RESULT — exact output from the displayed Queryflo rows

lead_id	campaign_name	source
301	Spring Launch	google_ads
302	Spring Launch	google_ads
303	Retention Webinar	email
304	Finance Retargeting	linkedin

ON follows the real leads.campaign_id to campaigns.id relationship.

Now You Try

Practice this concept

Marketing wants converted leads with their campaign name and lead source.

Available schema

marketing

Prefix tables with marketing.table_name.

lead_idcampaign_namesource

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

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

Intermediate business practice