create table t1 (n integer);
insert into t1 values (1);
insert into t1 values (2);
insert into t1 values (3);

-- First problem: it should be invalid to group by n and select rdb$db_key
select n, rdb$db_key from t1 group by n;

-- Second problem: error: column unknown DB_KEY is wrong raised
select n, rdb$db_key from t1 group by 1, 2;

-- Third problem: wrong values for rdb$db_key are returned
select n, t1.rdb$db_key from t1 group by 1, 2;