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Distinct But Reversed Pairs

Posted on 2009-07-15
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Last Modified: 2012-05-07
I have a table similar to:

colA     colB  colC colD
3          11      ...     ...
54        22
11        3
22        11
22        54

I need only distinct pairs, regardless of the order of the elements of a pair.  That is 3, 11 is a duplicate of 11,3.  I need only one of the two rows. Can be either one.  So the above table should be:

colA     colB
3          11
54        22
22        11

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Question by:studioEtc
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4 Comments
 
LVL 60

Expert Comment

by:chapmandew
ID: 24860047
so, you only care about the values in columna and columnb?
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LVL 37

Expert Comment

by:momi_sabag
ID: 24860061
select distinct cola,colb
from yourTable t1
where not exists (select 1 from yourtable t2 where t1.cola = t2.cola and t1.colb = t2.colb and cola>colb)
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Author Comment

by:studioEtc
ID: 24860566
I didn't think I had any problem with other columns but unfortunately I do.  When there are duplicates, I need to retain the row with the highest value in colC.
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LVL 37

Accepted Solution

by:
momi_sabag earned 500 total points
ID: 24873121
try this

select cola, colb, max(colc)
from  (select case when cola <= colb then cola else colb end as cola,
    case when cola <= colb then colb else cola end as colb, colc
    from yourTable ) t1
group by cola,colb
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