CareerCup

You can sort of do a union with a full outer join. It works as long as none of the values that you're joining overlap in each table. Try this:

SQL> create table table1 (name varchar2(100), id varchar2(100));

Table created.

SQL> create table table2 (name varchar2(100), id varchar2(100));

Table created.

SQL> insert into table1 (name, id) values ('table1 name', 'table1 id');

1 row created.

SQL> insert into table2 (name, id) values ('table2 name', 'table2 id');

1 row created.

SQL> select * FROM table1 full outer join table2 using (name, id);

NAME										     ID
--------------------------------------------------------------------------------------
table2 name									     table2 id
table1 name									     table1 id

Also, if you don't care about having the data in the same column you can do this:

SQL> select * FROM table1 t1 full outer join table2 t2 on 1 = 2

Using SQL queries that require 'OR' condition can be done either using JOIN or UNION

I don't think its possible because Join increases the number of column
while UNION increases the number of rows

I agree with previous comment. Otherwise, one would need more clarification from interviewer to know exactly what he intends to say since, this look pretty trivial.

The question is just a trap.
Join is a projection,union is a selection.
Join is used to perform a relation between 2 or more tables( or 2 instances of the same table), where as UNION just adds two result sets..

FULL OUTER JOIN is a UNION of LEFT JOIN and RIGHT JOIN

UNION and JOINS are both different concepts. Indeed you can do this to achieve the same results but both are different in terms of executions and plan creation.
JOIN affect the SELECTIVITY while UNION is considered while PROJECTING the data.

UNION and JOINS are both different concepts. Indeed you can do this to achieve the same results but both are different in terms of executions and plan creation.
JOIN affect the SELECTIVITY while UNION is considered while PROJECTING the data.

It is based on use case. It can be done.