combining and joining two tables with different no. of columns and same column name

Question

I tried to combined tables which is fus_shift and root table into a new table which is final table but it outputs like "ERROR at line 2: ORA-01789: query block has incorrect number of result columns". I tried also joining table as my alternative but it also outputs "ERROR at line 3: ORA-00918: column ambiguously defined". Is there another way to do combining and joining two table with different number of columns and having the same column name respectively? Thanks again:-)

code error:
create table final as
select * from fus_shift
union
select * from root;

code error:
select record_num,test_num,t_date,t_time,system_type,category,comments,val
from fus_shiftrpt,root
where record_num=record_num;

my tables:

                                 fus_shift Table


           Record_Num       test          date      time         system   
           -----------------------------------------------------------
                1          test15      08-11-12  13:20:01    sys23 
                2          test17      08-11-03  14:24:00    sys24
                3          test13      08-11-13  17:25:04    sys45
                4          test15      08-11-14  18:24:00    sys67
                5          test16      08-11-15  19:24:06    sys45


                                 root Table

           Record_Num      category   comments    validated by
           ---------------------------------------------------
                  1        dirt        checked        admin
                  2        prog        checked        admin
                  3        dirt        checked        pe
                  4        wires       checked        ee
                  5        prog        repair         admin

emphasized text

Answer 1

You certainly cannot apply "Union" to your tables. It can be applied only if both queries return same number (and of similar type) of columns.

You can join the two tables but would have to use "table alias" while joining since "record_num" field is common in both the tables. Here is the query that would work for you

select 
        table1.record_num,
        table1.test_num,
        table1.t_date,
        table1.t_time,
        table1.system_type,
        table2.category,
        table2.comments,
        table2.val
from 
       fus_shift table1,root table2
where 
       table1.record_num = table2.record_num;

Answer 2

I would use the following method:

SELECT * 
FROM fus_shift
INNER JOIN root ON root.record_num = fus_shift.record_num