>I have a table that looks something like this:
>
>

>groupnum          itemnum          quantity
>1                  10                  1
>2                  10                  1
>1                  17                  5
>2                  17                  5
>1                  23                  2
>1                  26                  1
>2                  26                  1
>1                  27                  3
>2                  27                  4
>1                  30                  0
>2                  30                  0
>2                  33                  1
>1                  36                  3
>2                  36                  5
>

>
>The table isn't really sorted, but we order it this way in queries. As you can see, most itemnums are found in groups 1 and 2, and usually have the same quantity. The user wants a query that returns those itemnums found in both groups, but with different quantities. In the above example, such a query would return:
>
>

>1                  27                  3
>2                  27                  4
>1                  36                  3
>2                  36                  5
>

>There are probably a few ways to do this, involving sequences of queries, but I wonder what would be the most efficient.
Why would

1                  17                  5
2                  17                  5

not included ?
Cetin