WITH T AS(
SELECT '1' A,'2' B,'3' C,'4' D,'5' E FROM dual UNION ALL
SELECT '21', '2', '3', '4', '5' FROM dual UNION ALL 
SELECT '1', '2', '3', NULL, NULL FROM dual UNION ALL
SELECT '1', '2', NULL, NULL, NULL  FROM dual UNION ALL 
SELECT '2', '1', '3', '4', '5' FROM dual UNION ALL 
SELECT '2', '1', '3', '4', NULL FROM dual 
)

SELECT * FROM 
(SELECT '@'||RTRIM(NVL2(A,A,'')||'@'||NVL2(B,B,'')||'@'||NVL2(C,C,'')||'@'||NVL2(D,D,'')||'@'||NVL2(E,E,''),'@')||'@' ALLSTR,A,B,C,D,E FROM T) T1,
(SELECT '@'||RTRIM(NVL2(A,A,'')||'@'||NVL2(B,B,'')||'@'||NVL2(C,C,'')||'@'||NVL2(D,D,'')||'@'||NVL2(E,E,''),'@')||'@' ALLSTR FROM T) T2
WHERE T1.ALLSTR <> T2.ALLSTR AND
      INSTR(T2.ALLSTR,T1.ALLSTR) = 1 ;

------解决方案--------------------

探讨

我的表现在算上id一共20个字段，比较其中两条数据，如果对应的字段都相等就算冗余，还有一种情况是这两条数据都有可能存在空字段，如果两条数据对应的非空字段都相等，而其中一条数据的非空字段多于另一条，则非空字段少的那条即为冗余。不知道明白没有


------解决方案--------------------

7楼的代码有点小问题，不支持1, null, 3, null, null格式的数据，我改进了代码，不过代码中使用了正则表达式，需要oracle 10g以上版本才支持.
SQL code

WITH T AS(
SELECT '1' A,'2' B,'3' C,'4' D,'5' E FROM dual UNION ALL
SELECT '21', '2', '3', '4', '5' FROM dual UNION ALL 
SELECT '1', '2', '3', NULL, NULL FROM dual UNION ALL
SELECT '1', '2', NULL, NULL, NULL  FROM dual UNION ALL 
SELECT '1',  NULL, NULL, '4', NULL  FROM dual UNION ALL 
SELECT '2', '1', '3', '4', '5' FROM dual UNION ALL 
SELECT '2', '1', '3', '4', NULL FROM dual 
)

SELECT * FROM 
(SELECT '@'||RTRIM(NVL2(A,A,'(.*)')||'@'||NVL2(B,B,'(.*)')||'@'||NVL2(C,C,'(.*)')||'@'||NVL2(D,D,'(.*)')||'@'||NVL2(E,E,'(.*)'),'@')||'@' ALLSTR,A,B,C,D,E FROM T) T1,
(SELECT '@'||RTRIM(NVL2(A,A,'')||'@'||NVL2(B,B,'')||'@'||NVL2(C,C,'')||'@'||NVL2(D,D,'')||'@'||NVL2(E,E,''),'@')||'@' ALLSTR FROM T) T2
WHERE T1.ALLSTR <> T2.ALLSTR AND
      REGEXP_LIKE(T2.ALLSTR,T1.ALLSTR)  ;