Filtering out unique rows in MySQL

So I've got a large amount of SQL data that looks basically like this:

user | src | dst
1    | 1   | 1
1    | 1   | 1
1    | 1   | 2
1    | 1   | 2
2    | 1   | 1
2    | 1   | 3

I want to filter out pairs of (sr开发者_StackOverflow社区c,dst) that are unique to one user (even if that user has duplicates), leaving behind only those pairs belonging to more than one user:

user | src | dst
1    | 1   | 1
1    | 1   | 1
2    | 1   | 1

In other words, pair (1,2) is unique to user 1 and pair (1,3) to user 2, so they're dropped, leaving behind only all instances of pair (1,1).

Edit: To clarify, I am not interested in the pairs that get filtered out, I need all the rows where the pairs are not unique.

Any ideas? The answers to the question below can find the non-unique pairs, but my SQL-fu doesn't suffice to handle the complication of requiring that they belong to multiple users as well.

How to select non "unique" rows

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My solution would be something like this (tested):

SELECT user, src, dst, COUNT(user) as num_of_users
FROM test
GROUP BY src, dst
HAVING num_of_users = 1

Edit: The following code produces the results that you provided in your example.

SELECT test.user, test.src, test.dst
FROM test
INNER JOIN
(
    SELECT user, src, dst, COUNT(DISTINCT user) as num_of_users
    FROM test
    GROUP BY src, dst
    HAVING num_of_users > 1
) as inner_sql
USING(src, dst)

Is this solution the one you are looking for? How is the performance?

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Join using EXISTS syntax

SELECT t1.*
FROM   table t1
WHERE EXISTS (SELECT 1 
              FROM   table t2 
              WHERE  t1.src   = t2.src 
               AND   t1.dst   = t2.dst
               AND   t1.user != t2.user)

Another option that MIGHT work (didn't test). If it works it would be more efficient:

SELECT user, src, dst
FROM   table
GROUP BY src, dst
HAVING COUNT(DISTINCT user) > 1

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May be with some group by?

something like

select user,src,dst,count(*) as c from table group by user,src,dst 
having c = 1