Detect duplicate multiple-row-pair in SQL, is it possible?

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April 27th, 2007, 06:42 AM

bmn

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Detect duplicate multiple-row-pair in SQL, is it possible?

In the table below column b contains parameters for column a.
Each a got 2 parameters b, thats why each a appears 2 times (on 2 rows).
I want to find duplicates of a. A duplicate a is defined as having the same b's as another a.
So in the table below a=1 and a=2 are a duplicate because they both got b=1 and b=2.
While a=3 and a=4 is "in the clear" so to speak.

Is it possible to do a SELECT where each row in the resultset means a duplicate?

Code:

+----+----+----+
| id | a  | b  |
+----+----+----+
|  1 |  1 |  1 |
|  2 |  1 |  2 |
|  3 |  2 |  1 |
|  4 |  2 |  2 |
|  5 |  3 |  1 |
|  6 |  3 |  3 |
|  7 |  4 |  2 |
|  8 |  4 |  3 |
+----+----+----+

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