SQL Joining Three or More Tables
The same pattern from Multiple JOINs, generalized — there's no hard limit on how many tables one query can chain together.
What & Why
Nothing about the previous lesson's technique changes when a fourth, fifth, or sixth table joins the chain — each new JOIN still connects to the combined result so far. Real reporting queries chaining 4-6 tables together are common; a dozen or more isn't unusual in large, well-normalized databases.
See How It Works
BUSINESS QUESTION
Marketing combines campaigns with both lead and email-send activity in one coverage report.
| 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 | 45000.00 | 2024-02-10 | 2024-04-15 | active | enterprise | |
| 3 | Finance Retargeting | 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 |
| id | campaign_id | 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 | 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 | US |
| id | campaign_id | sent_at | recipients | opens | clicks | unsubscribes | bounces |
|---|---|---|---|---|---|---|---|
| 201 | 1 | 2024-01-20 15:00:00+00 | 1200 | 540 | 180 | 9 | 24 |
| 202 | 2 | 2024-02-15 16:30:00+00 | 800 | 420 | 96 | 5 | 12 |
| 203 | 3 | 2024-03-18 13:00:00+00 | 1500 | 610 | 225 | 14 | 31 |
| 204 | 4 | 2024-04-08 14:00:00+00 | 0 | 0 | 0 | 0 | 0 |
EXAMPLE QUERY
SELECT
c.name,
COUNT(DISTINCT l.id) AS lead_count,
COUNT(DISTINCT e.id) AS send_count
FROM marketing.campaigns c
LEFT JOIN marketing.leads l ON l.campaign_id = c.id
LEFT JOIN marketing.email_sends e ON e.campaign_id = c.id
GROUP BY c.id, c.name
ORDER BY c.name;RESULT — exact output from the displayed Queryflo rows
| name | lead_count | send_count |
|---|---|---|
| Enterprise Search | 0 | 1 |
| Finance Retargeting | 1 | 1 |
| Retention Webinar | 1 | 1 |
| Spring Launch | 2 | 1 |
DISTINCT protects the independent lead and send counts from row multiplication.
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