What is the standard SQL Query to retrieve the intersection of tables?

Question

Selecting the union:

select * from table1 
union 
select * from table1_backup 

What is the query to select the intersection?

Answer 1

SELECT *
FROM table1
WHERE EXISTS
(SELECT *
FROM table1_backup
WHERE table1.pk = table1_backup.pk)

works

Answer 2

subqueries?! really?

to get the intersection of table1 and table2:

SELECT * FROM table1, table2 WHERE table1.pk=table2.pk;

Answer 3

In SQL Server intersect

select * from table1 
intersect
select * from table1_backup

Answer 4

"intersect" is also part of standard SQL.

Inner join gives a different answer.

Answer 5

An intersect on two identical tables a and b can be done in this manner:

SELECT a.id, a.name
FROM a INNER JOIN b
USING (id, name)

Answer 6

select distinct * from (select * from table1 union select * from table1_backup)