CareerCup

select email, count(email)
from table
group by email
having count(email) > 1

select distinct email
from table

it doesn't work if there is email exists more than twice.

select *
from email_table
group by email
having count(*) > 1

select email from email_table
where email NOT IN
(select email from email_table where count(email) = 1)

The "having count" solution works fine.

Here is another one:

select 
	ec.email 
from 
	(select 
		e.email, 
		count(e.mail) as email_count 
	from 
		email as e 
	group by e.email) as ec 
where 
	ec.email_cout > 1

select email_id from email_table where count(email_id)>1;

SELECT ROWID , EMAIL_ADDRESS FROM EMAIL_TABLE
WHERE ROWID NOT IN (SELECT MAX(ROWID) FROM EMAIL_TABLE GROUP BY EMAIL_ADDRESS)

select t1.email from
t as T1, t as T2
where T1.email == T2.email

SELECT EMAIL,COUNT(EMAIL)
FROM TABLE
GROUP BY EMAIL
HAVING COUNT(EMAIL)>1

If the table has only one column and this is a relational database, we cannot have duplicates in the table!

Could be solved with self join:
select distinct(a.email) from emails a join emails b on a.email=b.email and a.id!=b.id;

with dups_tbl as
(
select email,row_number() over(order by email) rn
from table
)
select distinct email from dups_tbl where rn > 1;

select distinct email
from table

select email 
from table
where email NOT IN (select distinct email from table)