SELECT * FROM (SELECT * FROM table_name)

select * from
                   (select  1  from Table_1
                    union all
                    select  2  from table_2
                    union all
                    select  3  from table_3) temp
                   order by  1 

CREATE CURSOR cur1 (rn1 n ( 1 ))
CREATE CURSOR cur2 (rn2 n ( 1 ))
CREATE CURSOR cur3 (rn3 n ( 1 ))

INSERT INTO Cur1 VALUES ( 1 )
INSERT INTO Cur1 VALUES ( 2 )
INSERT INTO Cur2 VALUES ( 3 )
INSERT INTO Cur3 VALUES ( 4 )
INSERT INTO Cur3 VALUES ( 5 )

SELECT * FROM Cur1 union ALL SELECT * FROM Cur2 UNION ALL SELECT * FROM Cur3 ORDER BY  1  DESC

CREATE CURSOR cur1 (rn1 n ( 1 ))
CREATE CURSOR cur2 (rn2 n ( 1 ))

INSERT INTO Cur1 VALUES ( 1 )
INSERT INTO Cur2 VALUES ( 1 )

SELECT t.* FROM (SELECT * FROM cur1) t INNER JOIN cur2 ON cur2.rn2 = t.rn1