INTERSECT vs inner join

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Accepted Answer

INTERSECT is the right tool when you want the overlap - rows present in both result sets. UNION would give you all emails from either table (with deduplication), not just the shared ones. EXCEPT would give you registered users who are NOT subscribers, which is the opposite of what we want. An equivalent using JOIN would be: SELECT r.email FROM registered_users r INNER JOIN newsletter_subscribers n ON r.email = n.email - both approaches work, but INTERSECT reads more clearly for this pattern.