SQL Joining Three or More Tables

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

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;