Removing redundant rows from db table - mysql

Question

I have a database table like the following (bad design I know, but there are a ton of rows like this):
person1 | person2 | counselor
Jane Doe | John Doe | Mary Smith
John Doe | Jane Doe | Mary Smith
Frank Jones| Ann Jones | Tom Jones
Ann Jones | Frank Jones | Tom Jones
I'm trying to figure out how to just select one of the 'unique' rows so that a result would look like:
person1 | person2 | counselor
Jane Doe | John Doe | Mary Smith
Frank Jones| Ann Jones | Tom Jones
I've tried various things like SELECT distinct and SELECT MIN(person1), etc., but am striking out.

Answer 1

You will have 6 permutations of (person1,person2,counselor) and you can use union with all of them. Finally use a where clause so only one row per combination will be returned.
Fiddle with sample data
select * from (
select person1,person2,counselor
from tablename
union
select person1,counselor,person2
from tablename
union
select person2,person1,counselor
from tablename
union
select person2,counselor,person1
from tablename
union
select counselor,person2,person1
from tablename
union
select counselor,person1,person2
from tablename) t
where person1 < person2 and person2 < counselor

Answer 2

SQL Fiddle Demo
I include a case where no reverse duplicated and also another case where person1 = person2, also include P2.* in select just for debug.
SELECT P1.person1, P1.person2, P1.counselor, P2.*
FROM patient P1
LEFT JOIN patient P2
ON P1.person1 = P2.person2
AND P1.person2 = P2.person1
AND P1.counselor = P2.counselor
WHERE
concat(P1.person1, P1.person2) <= concat(P2.person1, P2.person2)
OR P2.person1 is null
When P2 is NULL mean there isn't a reverse combination of person1, person2
But when the combination exists only choose the smaller one as string concatenation.

Answer 3

With ranked_records AS
(
select *,
ROW_NUMBER() OVER(Partition By person1, person2, counselor
Order By person) [ranked]
from address
)
select * from ranked_records
where ranked > 1
For more detail, like how to delete latest records and keep the older one.
For MySql and if you have Id, try this:
DELETE A1
From Address A1
Where Exists (Select * From Address A2
Where A2.person1= A1.person1
AND A2.person2 = A1.person2
AND A2.counselor = A1.counselor
AND A1.AddressID > A2.AddressID)