SQL INNER JOIN

Keeps only rows that have a match on BOTH sides — the strictest, most common join type, and usually what people mean by just 'JOIN.'

What & Why

INNER JOIN combines rows only when the join condition matches on both sides. In the Queryflo example, a product.feedback row is returned only when its feature_id matches a row in product.features; plain JOIN means the same thing as INNER JOIN in PostgreSQL.

See How It Works

BUSINESS QUESTION

Product wants feedback rows with known feature metadata.

id	user_id	feature_id	rating	nps_score	comment	created_at
1	101	1	5	9	Clear and useful	2024-01-25 12:15:00+00
2	102	2	4	NULL	Export worked well	2024-02-20 15:40:00+00
3	103	1	4	7	Helpful setup flow	2024-03-18 09:05:00+00
4	104	3	3	NULL	Needs clearer timing	2024-04-08 17:30:00+00

id	name	description	team	released_at	deprecated_at
1	Activation Checklist	Guides new users through setup	growth	2024-01-20	NULL
2	CSV Export	Exports report data	platform	2024-02-14	NULL
3	Invite Nudges	Prompts workspace collaboration	growth	2024-03-05	NULL
4	Legacy Dashboard	Original reporting surface	analytics	2023-08-10	2024-06-01

Trace the relationship row by row1× speed

product.features

id	name
1	Activation Checklist
2	CSV Export
3	Invite Nudges
4	Legacy Dashboard

feature.id = feedback.feature_id

product.feedback

id	feature_id	rating	created_at
1	1	5	2024-01-25 12:15:00+00
2	2	4	2024-02-20 15:40:00+00
3	1	4	2024-03-18 09:05:00+00
4	3	3	2024-04-08 17:30:00+00

Result set · 1 rows

name	rating	created_at
Activation Checklist	5	2024-01-25 12:15:00+00

Feedback 1 matches feature 1.

EXAMPLE QUERY

SELECT
  f.name,
  fe.rating,
  fe.created_at
FROM product.feedback fe
INNER JOIN product.features f ON f.id = fe.feature_id
ORDER BY fe.id;

Now You Try

Practice this concept

Product wants feedback rows with their matching feature metadata.

Available schema

product

Prefix tables with product.table_name.

nameratingcreated_at

product.features

Column	Type
id	integer
name	text
description	text
team	text
released_at	timestamp with time zone
deprecated_at	timestamp with time zone
internal_priority	integer

product.feedback

Column	Type
id	integer
user_id	integer
feature_id	integer
rating	integer
nps_score	integer
comment	text
created_at	timestamp with time zone
moderation_bucket	text

query.sql

Intermediate business practice