On 06.04.2016 o 22:03, 'stwizard' stwizard@... [firebird-support] wrote:

> SELECT DISTINCT P.AREA_CODE, P.PHONE_NO,
>
> (SELECT COUNT(*)
>
> FROM PHONE P2
>
> WHERE P2.PHONE_ID = P.PHONE_ID) AS CNT
>
> FROM PHONE P
>
> WHERE P.AREA_CODE IS NOT NULL
>
> GROUP BY 1, 2

[ ... ]

select A, B, (select count(*) from ...)
from ...

is not the same as

select A, B, count(*)
from ...

In the former case, the sub-select is not an aggregate function. It
simply calculates and returns a scalar (a single number), which is
treated just like one more "field" in selected records.
Therefore, for the GROUP BY to work correctly, you'd have to include the
third selected column (sub-select in your case) in the GROUP BY.
But that's not what you wanted, I suppose.
I guess what you really need is a normal grouped query:

select AREA_CODE, PHONE_NO, count(*)
from PHONE
where AREA_CODE is not null
group by 1, 2
having count(*) > 1

And that'll do the job.

Best regards
Tomasz