I have a table like below (using MS SQL server 2008)

```
Contact1    Contact2
--------    ---------
1234567890  9087654321
9087654321  1234567890
1234567890  1234567890
9087654321  9087654321
8989898989  9898989898
9898989898  8989898989

```

The values of Contact1 and Contact2 in 2nd row and 5th row is the swapped form of the values in 1st row and 6th row respectively. Also both the values are equal in 3rd and 4th row.

As there are several bogus entries, I need to remove those. The resulting table shall look like-

```
Contact1    Contact2
--------    ---------
1234567890  9087654321
8989898989  9898989898

```

I am a beginner to SQL and not getting any idea to proceed. Any help is appreciated.