find same record for multiple fields in mysql

Question

CREATE TABLE IF NOT EXISTS `userinfo` (
  `user_id` int(6) unsigned NOT NULL,
  `user_code` varchar(20),
  `party1_id` varchar(200),
  `party2_id` varchar(200),
  PRIMARY KEY (`user_id`)
) DEFAULT CHARSET=utf8;
INSERT INTO `userinfo` (`user_id`, `user_code`, `party1_id`, `party2_id`) VALUES
  ('1', '05B29E57', '1', ''),
  ('2', '05B29E58', NULL, '1'),
  ('3', '05B29E59', '2', ''),
  ('4', '05B29E60', NULL, '2'),
  ('5', '05B29E61', '3',''),
  ('6', '05B29E62', NULL, '3'),
  ('7', '05B29E63', NULL, '4'),
  ('8', '05B29E64', NULL, '5'),
  ('9', '05B29E65', NULL, '6'),
  ('10', '05B29E66', NULL, '7');

+---------+-----------+-----------+-----------+
| user_id | user_code | party1_id | party2_id |
+---------+-----------+-----------+-----------+
|       1 | 05B29E57  | 1         |           |
|       2 | 05B29E58  | NULL      |         1 |
|       3 | 05B29E59  | 2         |           |
|       4 | 05B29E60  | NULL      |         2 |
|       5 | 05B29E61  | 3         |           |
|       6 | 05B29E62  | NULL      |         3 |
|       7 | 05B29E63  | NULL      |         4 |
|       8 | 05B29E64  | NULL      |         5 |
|       9 | 05B29E65  | NULL      |         6 |
|      10 | 05B29E66  | NULL      |         7 |
+---------+-----------+-----------+-----------+

So i have above table as userinfo . Due to some reason i have to find the duplicate records for party1_id & party2_id.

I have tried below:

SELECT
  *
FROM userinfo u1
  JOIN userinfo u2
    ON u1.party1_id = u2.party2_id
WHERE IFNULL(u1.party1_id, 0) > 0
AND IFNULL(u1.party2_id, '') = ''

Fiddle: http://sqlfiddle.com/#!9/725eff/1

But it didn't give result in a way i want, it just returns 3 record. Is there a way to archive my expected output with sorting same as in my expected output.

Expected Output:

+---------+-----------+-----------+-----------+
| user_id | user_code | party1_id | party2_id |
+---------+-----------+-----------+-----------+
|       1 | 05B29E57  | 1         |           |
|       2 | 05B29E58  | NULL      |         1 |
|       3 | 05B29E59  | 2         |           |
|       4 | 05B29E60  | NULL      |         2 |
|       5 | 05B29E61  | 3         |           |
|       6 | 05B29E62  | NULL      |         3 |
+---------+-----------+-----------+-----------+

Answer 1

You could obtain the expected result using union

select t1.* 
from userinfo t1
inner join  (
    select a.party1_id apid, b.party2_id bpid
     FROM userinfo a
      JOIN userinfo b
        ON a.party1_id = b.party2_id
) t2 on t2.apid = t1.party1_id
UNION 
select t1.* 
from userinfo t1
inner join  (
    select a.party1_id apid, b.party2_id bpid
     FROM userinfo a
      JOIN userinfo b
        ON a.party1_id = b.party2_id
) t2 on t2.apid = t1.party2_id
order by user_id 

http://sqlfiddle.com/#!9/725eff/17

for performance be sure you have al least thiese indexes

idx1  table userinfo columns (party1_id, party2_id)

idx2 table userinfo columns (party2_id, party1_id)

Answer 2

You can give a try following.

select * from userinfo where 
party1_id  in (
  SELECT
  u1.party1_id
FROM userinfo u1
  JOIN userinfo u2
    ON u1.party1_id = u2.party2_id
WHERE IsNULL(u1.party1_id, 0) > 0
AND IsNULL(u1.party2_id, '') = '') or party2_id in ( SELECT
  u1.party1_id
FROM userinfo u1
  JOIN userinfo u2
    ON u1.party1_id = u2.party2_id
WHERE IsNULL(u1.party1_id, 0) > 0
AND IsNULL(u1.party2_id, '') = '')

Answer 3

Try with below query:

SELECT
  *
FROM userinfo u1
  where
  u1.party1_id in (select distinct u2.party2_id from userinfo u2) 
  or 
  u1.party2_id in (select distinct u3.party1_id from userinfo u3)

Below is the output I get in your fiddle for above query:(order by can be applied to any column)

user_id     user_code   party1_id   party2_id
1           05B29E57    1   
2           05B29E58    (null)      1
3           05B29E59    2   
4           05B29E60    (null)      2
5           05B29E61    3   
6           05B29E62    (null)      3