Oracle Sql NOT NULL xor NULL？

Question

我正在选择一组记录，并且我想过滤XOR逻辑中的一列- IS NOT NULL xor IS NULL。

--basic
SELECT make, model
FROM cars

results
--------
ford   taurus
ford   (null)
toyota camry
toyota (null)
honda  (null)

--Obviously XOR is not a real Oracle operator
--This is what I'm trying to do..
SELECT make, model
FROM cars
WHERE model IS NOT NULL
  XOR model IS NULL 

results (pulls records where model IS NOT NULL, falling back to NULL if necessary)
--------
ford   taurus
toyota camry
honda  (null)

有谁能给我一些关于如何达到我想要的结果的见解？我正在努力解决这个问题！

非常感谢！

Answer 1

SELECT  make, model
FROM    (
        SELECT  c.*,
                ROW_NUMBER() OVER (PARTITION BY make ORDER BY model NULLS LAST) AS rn
        FROM    cars c
        )
WHERE   NOT (rn > 1 AND model IS NULL)

Answer 2

SELECT make, model
FROM cars 
WHERE model IS NOT NULL
UNION -- Add makes that don't have any specific model
SELECT make, model 
FROM cars 
WHERE make NOT IN 
  (SELECT make
  FROM cars 
  WHERE model IS NOT NULL)

Answer 3

我最初支持Klas Lindbäck的答案，但现在我想知道这是否会给出预期的结果：

SELECT make, model
  FROM Cars 
 WHERE model IS NOT NULL
UNION 
SELECT make, NULL
  FROM Cars 
MINUS
SELECT make, NULL
  FROM cars 
 WHERE model IS NOT NULL;