ActiveRecord equivalent of FULL OUTER JOIN
Need a FULL OUTER JOIN in Rails? Learn why ActiveRecord doesn’t support it natively and the safest Postgres + UNION workarounds for production.
9 min read
Joins & Associations
Deep dives into SQL JOIN behavior and how it maps to Rails associations, including LEFT JOIN pitfalls, join conditions, and unexpected query results.
7 Production-Safe Ways to Do a SQL `CROSS JOIN` in Rails (and When You Actually Should)
Need an ActiveRecord cross join? Learn when SQL CROSS JOIN is justified, how to express it in Rails safely, and how to avoid row explosions in production.
7 min read
LEFT JOIN + WHERE in ActiveRecord: The Trap That Turns It Into INNER JOIN
LEFT JOIN queries often break the moment you add a WHERE on the joined table—silently turning into INNER JOIN behavior. Learn the correct Rails patterns (ON vs WHERE, scoped associations, where.missing/where.associated, EXISTS) and how to verify generated SQL.
5 min read
ActiveRecord Equivalent of SQL CROSS JOIN (And When You Actually Need It)
How to do a SQL CROSS JOIN from ActiveRecord safely: when it’s the right tool, how to express it without losing bind params, and how to avoid accidental Cartesian products.
4 min read
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ActiveRecord INNER JOIN with Multiple Conditions (Without Lying to Yourself)
How to express INNER JOINs with multiple conditions in Rails without changing semantics by accident. Learn when Rails puts predicates in WHERE vs ON, how merge/default_scope can surprise you, and the patterns that stay correct when you later switch to LEFT JOIN.
5 min read