MySQL Forums :: Newbie :: Problem with 2 solutions

Hi, I have a difficulty about two queries. I think are the same but it does not show me the same resultt

1. The first solution which is correct:
select ua.Email from interest i
join useraccount ua on i.UserAccountId = ua.Id
where i.SystemId = 'goldendeals.gr'
and i.StatusCode in (301, 302, 312)
and (select systemId from newslettersubscription where EmailAddress =ua.email order by SubscriptionDate asc limit 1) = 'Kati1.gr';

the second where there is the mistake:
Α.
select ns.EmailAddress,
( select systemId from newslettersubscription where EmailAddress =ua.email order by SubscriptionDate asc limit 1) as buyerSystem
from useraccount ua
join newslettersubscription ns on ns.EmailAddress=ua.Email and ns.SystemId = ua.SystemId
where ua.systemId='Kati1.gr' ;

Β.
select ua.Email from useraccount ua
join interest i on ua.Id = i.UserAccountId
where i.StatusCode in (302,301,312) and ua.SystemId='Kati2.gr'
and ua.Email in (
'skepsys@otenet.gr',
'kalliantra79@yahoo.gr',
'tychwn@hotmail.com',
'panvas85@hotmail.com',
...
'eblatsiou@yahoo.gr');

in the second solution I run Α. query and then I run Β.

Please find me the mistake
Thank you in advance !