SQL Query Help

I have two tables: User table and Order table

Let say user table has following records

usera1,emaila
usera2,emaila
userb,emailb
userc1,emailc
userc2,emailc
userd,emaild

Order table has following two records
usera1,emaila
userb,emailb
userc1,emailc
userc2,emailc


As you see there are two user accounts for each emaila and emailc
However usera2 using emaila is just duplicate account with no associated record in order table.
How can I get SQL query that will give me list of such duplicate accounts?
Please note userd is not in the order table but there us no duplicate in the user table so it should not be included in query result.

Basically query should result user account that is not in order table and that has another account using same email.
shwekhawAsked:
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bleach77Connect With a Mentor Commented:
This SQL do:
1.  Get result of duplicate email.
2.  Get the user id associated with the email.
3.  Eliminate the user that is in "order" table.

I don't really get what you really want. But this is based on mahome answer.
SELECT u2.userid, u2.email
FROM (SELECT email FROM user GROUP BY email HAVING count(userid) > 1) u LEFT JOIN user u2 ON u.email=u2.email
WHERE u2.userid NOT IN (SELECT userid FROM order)

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mahomeCommented:
Try this:

select * from user u
where u.user_name not in (select o.user_name from order o)
and u.email in (
  select u2.email from user u2
  group by u2.email
  having count(*) > 1
)

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shwekhawAuthor Commented:
It freezes up, User table has about 35000 records. Orde table has over 50000 records
I am not sure the problem is table size or syntax.
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shwekhawAuthor Commented:
I tried running just the following and it is ok.
select * from user u
where u.user_name not in (select o.user_name from order o)

I also try running just
select u2.email from user u2
  group by u2.email
  having count(*) > 1

It seems ok too. But if I combine into one syntax, it is taking forever.
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shwekhawAuthor Commented:
The part that is not working or taking so long to execute is

select * from user u
where u.email in (
  select u2.email from user u2
  group by u2.email
  having count(*) > 1
)

How can I get arounf this?
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mahomeCommented:
do you have an index on email?
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