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Thread: COUNT func

COUNT func

From
Oleg Lebedev
Date:
Hi,
I am trying to count the number or rows in a table with similar field
values. I want to do it in one table scan.
In other words, say I want to count the number of rows in Person table,
having age equal to 40, and the number of rows with status as 'married'.
I want Person table to be scanned only once during this query.
So, basically I want to do the following:
SELECT COUNT(age=40), COUNT(status='married')
FROM Person;

I tried to use aggregate functions with group by and having clauses, but
I still can't figure it out (probably because of the lack of
experience).
Please help.
Thanks,

Oleg

Re: COUNT func

From
Oleg Lebedev
Date:
It worked!
I checked the query plan it generates, and it's really a one-pass scan.
thanks,

Oleg

Stephan Szabo wrote:

> On Thu, 18 Oct 2001, Oleg Lebedev wrote:
>
> > Hi,
> > I am trying to count the number or rows in a table with similar field
> > values. I want to do it in one table scan.
> > In other words, say I want to count the number of rows in Person table,
> > having age equal to 40, and the number of rows with status as 'married'.
> > I want Person table to be scanned only once during this query.
> > So, basically I want to do the following:
> > SELECT COUNT(age=40), COUNT(status='married')
> > FROM Person;
> >
> > I tried to use aggregate functions with group by and having clauses, but
> > I still can't figure it out (probably because of the lack of
> > experience).
>
> Maybe something like [untested]
> SELECT SUM(case when age=40 then 1 else 0 end),
>        SUM(case when status='married' then 1 else 0 end)
>  FROM PERSON;
> will work?

Re: COUNT func

From
Stephan Szabo
Date:
On Thu, 18 Oct 2001, Oleg Lebedev wrote:

> Hi,
> I am trying to count the number or rows in a table with similar field
> values. I want to do it in one table scan.
> In other words, say I want to count the number of rows in Person table,
> having age equal to 40, and the number of rows with status as 'married'.
> I want Person table to be scanned only once during this query.
> So, basically I want to do the following:
> SELECT COUNT(age=40), COUNT(status='married')
> FROM Person;
> 
> I tried to use aggregate functions with group by and having clauses, but
> I still can't figure it out (probably because of the lack of
> experience).

Maybe something like [untested]
SELECT SUM(case when age=40 then 1 else 0 end),       SUM(case when status='married' then 1 else 0 end)FROM PERSON;
will work?

Re: COUNT func

From
Bhuvan A
Date:

hi,
try this too..

select count(*),age,status from person  where age=40 and
status='MARRIED' group by age,status;    
Regards,
Bhuvaneswar.

On Oct 18, Oleg Lebedev wrote:

> Hi,
> I am trying to count the number or rows in a table with similar field
> values. I want to do it in one table scan.
> In other words, say I want to count the number of rows in Person table,
> having age equal to 40, and the number of rows with status as 'married'.
> I want Person table to be scanned only once during this query.
> So, basically I want to do the following:
> SELECT COUNT(age=40), COUNT(status='married')
> FROM Person;
> 
> I tried to use aggregate functions with group by and having clauses, but
> I still can't figure it out (probably because of the lack of
> experience).
> Please help.
> Thanks,
> 
> Oleg
> 
> 
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