Select 'aa' a,'bb' b,'cc' c,NULL d,NULL e,NULL f From dual UNION ALL Select NULL a,NULL b,NULL c,'dd' e,'ee' e,'ff' f From dual 我需要得到的结果集效果是 SELECT 'aa' a,'bb' b,'cc' c, 'dd' e,'ee' e,'ff' f From dual 应该怎么写?
SELECT MAX(a), MAX(b), MAX(c), MAX(d), MAX(e), MAX(f) FROM (SELECT 'aa' a, 'bb' b, 'cc' c, NULL d, NULL e, NULL f FROM dual UNION ALL SELECT NULL a, NULL b, NULL c, 'dd' e, 'ee' e, 'ff' f FROM dual);
select max(a), max(b), max(c), max(d), max(e), max(f) from (Select 'aa' a, 'bb' b, 'cc' c, NULL d, NULL e, NULL f From dual UNION ALL Select NULL a, NULL b, NULL c, 'dd' e, 'ee' e, 'ff' f From dual)
FROM (SELECT 'aa' a, 'bb' b, 'cc' c, NULL d, NULL e, NULL f
FROM dual
UNION ALL
SELECT NULL a, NULL b, NULL c, 'dd' e, 'ee' e, 'ff' f FROM dual);
from (Select 'aa' a, 'bb' b, 'cc' c, NULL d, NULL e, NULL f
From dual
UNION ALL
Select NULL a, NULL b, NULL c, 'dd' e, 'ee' e, 'ff' f From dual)