Re: count(*) vs count(id)

On 2/1/21 4:53 PM, Matt Zagrabelny wrote:
> Greetings,
>
> Is there a preferred method of counting rows?
>
> count(*) vs count(field_name)
>
> I have used count(*) for a long time and am hitting an inconsistency. At
> least it is an inconsistency to me (I'm sure there is an explanation)...
>
> INCORRECT OUTPUT (not desired results)
> $ select calendar.entry, count(*)  from
> generate_series('2020-01-01'::date, '2021-01-10'::date, '1
> day'::interval) as calendar(entry) left join call_records on
> calendar.entry = call_records.timestamp::date group by calendar.entry;
> [...]
>  2020-08-30 00:00:00-05 │     1
>  2020-08-31 00:00:00-05 │     1
> [...]
>
> CORRECT OUTPUT (desired results)
> $ select calendar.entry, count(id)  from
> generate_series('2020-01-01'::date, '2021-01-10'::date, '1
> day'::interval) as calendar(entry) left join call_records on
> calendar.entry = call_records.timestamp::date group by calendar.entry;
> [...]
>  2020-08-30 00:00:00-05 │     0
>  2020-08-31 00:00:00-05 │     0
> [...]
>
> What am I missing between count(*) and count(id)?
>
> Thanks for any help!
>
> -m

You got one null from count(*) likely.