Обсуждение: group by does not show error

I am using Postgresql 9.1.0.

I found that following GROUP BY query works in my DB :-

   \d t1
      Table "public.t1"
 Column |  Type   | Modifiers
--------+---------+-----------
 i      | integer | not null
 nam    | text    |
Indexes:
    "t1_pkey" PRIMARY KEY, btree (i)


   select i,nam
   from t1
   group by i;
  
    i | nam
---+-----
(0 rows)


I think the query should show an error as I did not maintain group by standard.
Does anyone know why it does not show syntax error?

AI Rumman wrote on 24.03.2012 09:06:
> I am using Postgresql 9.1.0.
>
> I found that following GROUP BY query works in my DB :-
>
>     \d t1
>        Table "public.t1"
>   Column |  Type   | Modifiers
> --------+---------+-----------
>   i      | integer | not null
>   nam    | text    |
> Indexes:
> "t1_pkey" PRIMARY KEY, btree (i)
>
>
>     select i,nam
>     from t1
>     group by i;
>
>      i | nam
> ---+-----
> (0 rows)
>
>
> I think the query should show an error as I did not maintain group by standard.
> Does anyone know why it does not show syntax error?

That's an enhancement in 9.1

As you included the primary key in the group by clause the rows are going to be unique anyway and no additional columns
arenecessary.