select a.* , null title , null desption from a
union all
select b.id , null name , null age , b.title , null desption from b
union all
select c.id , null name , null age , null title , c.desption from c

------解决方案--------------------
SELECT t.id,a.name,a.age,b.title,b.desption
(SELECT ID FROM a  UNION  
SELECT ID FROM b UNION  
SELECT ID FROM c) t
LEFT JOIN a ON t.ID=a.ia
LEFT JOIN b ON t.id=b.id
LEFT JOIN c ON t.id=c.id

------解决方案--------------------
create view myview
as
id name age title desption
select id, name, age, null as title, null as desption from a
union all
select id,null as name, null as age, title,null as desption from b
union all
select id, null as name,null as age, null as title, desption from c


------解决方案--------------------
实测数据：
SQL code

CREATE TABLE A
(
    ID NUMBER(4),
    NAME VARCHAR2(20),
    Age NUMBER(2)
);
INSERT INTO A VALUES(1, 'AA', 12);
INSERT INTO A VALUES(2, 'BB', 20);

CREATE TABLE B
(
    ID NUMBER(4),
    Title VARCHAR2(20)
);
INSERT INTO B VALUES(1, 'GGG');
INSERT INTO B VALUES(2, 'FFF');

CREATE TABLE C
(
    ID NUMBER(4),
    Desption VARCHAR2(20)
);

INSERT INTO C VALUES(1, 'JJJ');
INSERT INTO C VALUES(2, 'KKK');
CREATE VIEW ViewABC AS 
(SELECT ID, NAME, Age, NULL  AS Title, NULL AS Desption FROM A
UNION ALL
SELECT NULL AS ID, NULL AS NAME, NULL AS Age, Title, NULL AS Desption FROM B
UNION ALL
SELECT NULL AS ID, NULL AS NAME, NULL AS Age, NULL AS Title, Desption FROM C)