请教一个左连接有关问题

请教一个左连接问题
SELECT *
FROM table1 t1 LEFT OUTER JOIN table2 t2
  ON t1.a = t2.c
ORDER BY t1.a

如果t1.a，t2.c都是null，怎么关联起来？


------解决方案--------------------
JUST TRY IT ..

SQL code

SELECT *  FROM TABLE1 T1  LEFT OUTER JOIN TABLE2 T2 ON NVL(T1.A, 0) = NVL(T2.C, 0) ORDER BY T1.A;