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Query help

Author

Topic

mavershang
Posting Yak Master

111 Posts

Posted - 2011-09-13 : 18:06:26

Hi there. I have a table like
Col1 Col2
1 100
2 121
3 130
...
100 1
...
121 2
...

Now what I want is: if there are two rows with Col1 and Col2 exchanged, then just save one of them.
For above table, I just want
1 100
2 121
3 130

Thanks in advance.

singularity
Posting Yak Master

153 Posts

Posted - 2011-09-13 : 19:58:34

[code]
select col1, col2
from yourtable
union
select col2, col1
from yourtable
[/code]

mavershang
Posting Yak Master

111 Posts

Posted - 2011-09-14 : 11:18:11

Thanks for replying. But your query won't work since it actually selects all rows.

quote:
Originally posted by singularity

select col1, col2
from yourtable
union
select col2, col1
from yourtable

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-09-14 : 11:53:05

so you're trying to insert this to someother table?

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

mavershang
Posting Yak Master

111 Posts

Posted - 2011-09-14 : 12:07:24

Not really, just a selection

quote:
Originally posted by visakh16

so you're trying to insert this to someother table?

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

Lamprey
Master Smack Fu Yak Hacker

4614 Posts

Posted - 2011-09-14 : 12:42:51

I was goofing around and this seems to work if you only have 1 or 2 "duplicates." If you ahve more, then you'll need to do more to "uniqueify" the starting datasets:

DECLARE @Foo TABLE (C1 INT, C2 INT)

INSERT @Foo (C1, C2)
VALUES
    (1, 100),
    (2, 121),
    (2, 130),
    (121, 2),
    (3, 99),
    (99, 3),
    (120, 10)


SELECT 
    C1, 
    C2,
    RowNum
FROM
    (        
        SELECT 
            A.C1, 
            A.C2, 
            (
                ROW_NUMBER() OVER (ORDER BY A.C1, A.C2) 
                - ROW_NUMBER() OVER (ORDER BY B.C1, B.C2) 
            ) AS RowNum
        FROM 
            @Foo AS A
        LEFT JOIN
            @Foo AS B
            ON A.C1 = B.C2
            AND A.C2 = B.C1    
    ) AS A    
WHERE 
    RowNum >= 0

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