Analise os dois comandos SQL a seguir.

SELECT T1.A AS X, T2.A AS Y
FROM T1 LEFT JOIN T2 ON T1.A = T2.A
UNION ALL
SELECT T1.A AS X, T2.A AS Y
FROM T1 RIGHT JOIN T2 ON T1.A = T2.A

SELECT T1.A AS X, T2.A AS Y
FROM T1 FULL JOIN T2 ON T1.A = T2.A

Executados no SQL Server, os dois comandos acima produzem resultados equivalentes: