SQL Non-Equi JOIN

Any join whose condition uses something other than = — the general family the JOINs with Comparison Operators lesson introduced, now named explicitly.

What & Why

"Non-equi join" is simply the name for any join whose ON condition doesn't use plain equality — >, <, >=, <=, or != all qualify. It's a category label for the comparison-operator technique from two lessons ago, not a different SQL keyword.

See How It Works

BUSINESS QUESTION

SaaS finance matches each account to invoices whose amount is at least that account's MRR.

id	name	plan	mrr	created_at	churned_at	country	employee_count	industry
1	Acme Labs	growth	240.00	2024-01-08 10:00:00+00	NULL	US	45	software
2	Northstar Co	starter	90.00	2024-02-12 09:30:00+00	2024-05-18 12:00:00+00	CA	18	services
3	Atlas Works	scale	480.00	2024-03-04 15:10:00+00	NULL	GB	120	manufacturing
4	Bright Path	growth	180.00	2024-04-19 11:45:00+00	NULL	US	62	education

id	account_id	amount	status	due_date	paid_at
10	1	240.00	paid	2024-02-01	2024-01-29 13:00:00+00
11	1	260.00	paid	2024-03-01	2024-02-28 16:30:00+00
12	2	90.00	overdue	2024-03-15	NULL
13	3	480.00	open	2024-04-01	NULL

EXAMPLE QUERY

SELECT
  a.name,
  a.mrr,
  i.id AS invoice_id,
  i.amount
FROM saas.accounts a
JOIN saas.invoices i
  ON i.account_id = a.id
 AND i.amount >= a.mrr
ORDER BY a.name, invoice_id;

RESULT — exact output from the displayed Queryflo rows

name	mrr	invoice_id	amount
Acme Labs	240.00	10	240.00
Acme Labs	240.00	11	260.00
Atlas Works	480.00	13	480.00
Northstar Co	90.00	12	90.00

The account key matches first; the inequality then keeps invoices meeting MRR.

Now You Try

Practice this concept

SaaS finance wants invoices whose amount is at least the MRR of their own account.

Available schema

saas

Prefix tables with saas.table_name.

account_namemrrinvoice_idamount

saas.accounts

Column	Type
id	integer
name	text
plan	text
mrr	numeric
created_at	timestamp with time zone
churned_at	timestamp with time zone
country	text
employee_count	integer
industry	text
customer_segment_v2	text

saas.invoices

Column	Type
id	integer
account_id	integer
amount	numeric
status	text
due_date	date
paid_at	timestamp with time zone
internal_invoice_batch	text

query.sql

Intermediate business practice