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.

Intermediate business practice