Re: challenging query

> 
> Consider the following table:
> 
> A    B    C    D    select?
> -------------------------------
> 1    FOO    A1    100    n
> 1    BAR    Z2    100    n
> 2    FOO    A1    101    y
> 2    BAR    Z2    101    y
> 3    FOO    A1    102    y
> 4    BAR    Z2    99    y
> 5    FOO    A1    99    n
> 6    BAR    Z2    98    n
> 7    FOO    AB    103    y
> 7    BAR    ZY    103    y
> 
> This table has the idea of "groups", that is, a group is defined as
> all of the words from B that have the same number A.  The values in
> column C also matter- we want to select both groups A=7 and A=1 since
> they contain different values C.  Note that the groups defined by A=1
> and A=3 are distinct- they do not contain the same number of words
> from B, so we want to select them both.  Also note that D is datetime,
> and all the rows with the same number A will have the same D (this is
> actually ensured by a single row in another table.)
> 
> I want to select all of the numbers A which define distinct groups and
> have the highest datetime D.  Is this possible in a SQL query?
> 
Now that I've read your request more attentively, I understand what 
you want. But I have to admit I have no idea how to word the query, 
I even don't know if it's possible at all. 
Regards, Christoph