This is solution:
select * from tabella A where Group_ID in (Select min(Group_ID) in tabella B
where B.ID=A.ID);

-------Messaggio originale-------

Da: 'Leyne, Sean' Sean@... [firebird-support]
Data: 29/07/2015 18.59.03
A: firebird-support@yahoogroups.com
Oggetto: [firebird-support] RE: Possible to use FIRST 1 inside a group by?


Maya,

> Might not be the most efficient method, but this works:

Unfortunately, it is least efficient method -- you will read each table row
n^2 times

Try:

SELECT
T.ID
T.GroupID
T2.FKCode
T2.Value
FROM (
select MIN (ID) as ID, GroupID
from MyTable
GROUP BY GroupID
) T
JOIN MyTable T2 ON T2.ID = T.ID

Sean





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