SQL Server → PostgreSQL

CROSS APPLY vs LATERAL JOIN: Correlated Subqueries in Migration

SQL Server CROSS APPLY and OUTER APPLY map to LATERAL JOIN in PostgreSQL. Guide with TOP-per-partition examples.

APPLY runs the right-side subquery for each left row and can reference outer columns. In PostgreSQL, LATERAL does the same — CROSS APPLY becomes CROSS JOIN LATERAL, OUTER APPLY becomes LEFT JOIN LATERAL.

Translation

PostgreSQL

SELECT c.name, p.amount
FROM customers c
CROSS JOIN LATERAL (
  SELECT amount FROM payments
  WHERE customer_id = c.id
  ORDER BY date DESC
  LIMIT 1
) p;

Analisador de Impacto

APPLY appears in complex reports and breaks on first PostgreSQL execution. Map every usage in diagnostics.

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