如果性能不重要，请尝试vertica flex表：

DROP TABLE IF EXISTS allcols;                            
DROP TABLE IF EXISTS allbut1;
DROP TABLE IF EXISTS allbut4;

CREATE FLEX TABLE allcols();
INSERT INTO allcols(col1,col2,col3,col4)
          SELECT  1,  2,  3,  4
UNION ALL SELECT 11, 12, 13, 14
;

CREATE FLEX TABLE allbut1();
INSERT INTO allbut1(col2,col3,col4)
          SELECT  22, 23, 24
UNION ALL SELECT  32, 33, 34
;

CREATE FLEX TABLE allbut4();
INSERT INTO allbut4(col1,col2,col3)
          SELECT  21, 22, 23
UNION ALL SELECT  31, 32, 33
;
COMMIT;
\pset null (null)
          SELECT col1,col2,col3,col4 FROM allcols
UNION ALL SELECT col1,col2,col3,col4 FROM allbut1
UNION ALL SELECT col1,col2,col3,col4 FROM allbut4
;
-- out   col1  | col2 | col3 |  col4  
-- out --------+------+------+--------
-- out  1      | 2    | 3    | 4
-- out  11     | 12   | 13   | 14
-- out  (null) | 22   | 23   | 24
-- out  (null) | 32   | 33   | 34
-- out  21     | 22   | 23   | (null)
-- out  31     | 32   | 33   | (null)

如果表有主键，可以尝试：

select . . . ,
       (select colx   -- no table alias!
        from t t2
        where t2.primary_key = t.primary_key
       ) as colx
from t cross join
     (select null as colx) x;

作用域规则在sql中的工作方式是 colx 将从子查询中“满足”-if t 有列。否则，它将到达外部查询并选择 x ，因为 t 也不会有专栏。