Types of Set Operations

1 Intersect: unique rows common in both tables.

select * from one
intersect
select * from two;

Inner Join
select ...
from one a
inner join two b
on  a.key = b.key

2 Union: unique rows from both tables.
select * from one
union
select * from two;

Left Join
select ...
from one a
left join two b
on  a.key = b.key

select ...
from one a
left join two b
on  a.key = b.key
where b.key is NULL

3 Outer Union: all rows from both tables, unique or non-unique are selected.
select * from one
outer union
select * from two;

Outer Join
select ...
from one a
full outer join two b
on  a.key = b.key

4 Except: unique rows from the first table that are not in the second table.

select * from one
except
select * from two;

Outer Join

select ...
from one a
full outer join two b
on  a.key = b.key
where a.key is NULL
and b.key is NULL