Anda selalu dapat mencoba sesuatu seperti:
set heading off;
select 'NAME1' name1, 'NAME2' name2, 'NAME3' name3 from dual
union all
select a.col1 as name1, a.col2 as name2, b.col3 as name3
from tab1 a, tab2 b
where <join condition>;
ETA:Jika jenis kolom yang dikembalikan oleh kueri utama tidak semuanya string, Anda harus mengonversinya secara eksplisit. Ini contohnya:
create table test1 (col1 number,
col2 date,
col3 varchar2(10),
col4 clob);
insert into test1 values (1, sysdate, 'hello', 'hello');
commit;
select 'col1' col1, 'col2' col2, 'col3' col3, 'col4' col4 from dual
union all
select col1, col2, col3, col4
from test1;
*
Error at line 1
ORA-01790: expression must have same datatype as corresponding expression
set heading off;
select 'col1' col1, 'col2' col2, 'col3' col3, to_clob('col4') col4 from dual
union all
select to_char(col1), to_char(col2, 'dd/mm/yyyy hh24:mi:ss'), col3, col4
from test1;
col1 col2 col3 col4
1 05/08/2015 11:23:15 hello hello
