Re: Please advice on query optimization

Much easier to follow bottom-posting but I'll be consistent here.

It seems like you want a join of 4 sub-queries.

SELECT *
FROM unique_day_employee
LEFT JOIN aggregates_query USING (day, employee)
LEFT JOIN first_signin_query USING (day, employee)
LEFT JOIN last_signin_query USING (day, employee)

Where the definition of the first/last sign-in sub-queries are like

SELECT DISTINCT ON (day, employee) day, employee, time, device FROM tbl
ORDER BY day, employee, time ASC -- first
SELECT DISTINCT ON (day, employee) day, employee, time, device FROM tbl
ORDER BY day, employee, time DESC -- last

David J.

On Thu, Apr 20, 2017 at 10:35 AM, Muhannad Shubita <
muhannadshubita(at)gmail(dot)com> wrote:

> Thanks Samed,
>
> one more question, what if I had other columns that cannot be used with an
> aggregate function (TEXT-based for example) but still needed to be paired
> with the first & last sign in? for instance, a randomly generated md5-ed ID
> by the sign in device that needs to be displayed as a reference:
>
> Day Employee Total-Hours First-Sign-In device-id-of-first-sign-in Last-Sign-In
> device-id-of-last-sign-in
>
> 20/4 emp1 4 8:22 202cb962ac5.. 3:25 152d234b70..
>
>
> On Thu, Apr 20, 2017 at 9:18 PM, Samed YILDIRIM <samed(at)reddoc(dot)net> wrote:
>
>> Hi Muhannad,
>>
>> Did you try using MIN and MAX function? I guess that following query
>> solves your problem.
>>
>> select employee_id, day, sum(total_hours) as total_hours, (select name
>> from employee where id = employee_id) as emp_name, *min(sign_in) as
>> first_sign_in, max(sign_in) as last_sign_in*
>> from bioemployee where sign_in BETWEEN X and Y GROUP BY employee_id, day
>> ORDER BY day;
>>
>> Best regards.
>>
>>
>>
>>
>> İyi çalışmalar.
>> Samed YILDIRIM
>>
>>
>>
>> 20.04.2017, 19:56, "Muhannad Shubita" <muhannadshubita(at)gmail(dot)com>:
>>
>> Good day,
>>
>> I have a table with biometric info about employees (let's call it
>> bioemployee):
>>
>> id serial not null -- primary key
>> employee_id -- foreign key references employee table
>> day char(8) -- YY-MM-DD
>> sign_in TIMESTAMP
>> total_hours INTEGER
>>
>> I want to display details grouped by day & employee Id, for example:
>>
>>
>> Day Employee Total-Hours First-Sign-In Last-Sign-In
>>
>> 20/4 emp1 4 8:22 3:25
>> 21/4 emp1 7 9:00 4:11
>> 21/4 emp2 2 11:00 01:11
>>
>>
>> I created a pgsql function to get the details through the below query:
>>
>> select employee_id, day, sum(total_hours) as total_hours, (select name
>> from employee where id = employee_id) as emp_name
>> from bioemployee where sign_in BETWEEN X and Y GROUP BY employee_id, day
>> ORDER BY day;
>>
>> now the problem is with getting First-Sign-In & Last-Sign-In per group
>> (employee & day), I have currently implemented it in a FOR loop:
>>
>> for RECORD in query LOOP
>> --First-Sign-In
>> select sign_in from bioemployee where employee_id = -- and day = -- and
>> sign_in BETWEEN X and Y ORDER BY sign_in LIMIT 1;
>> --Last-Sign-In
>> select sign_in from bioemployee where employee_id = -- and day = -- and
>> sign_in BETWEEN X and Y ORDER BY sign_in DESC LIMIT 1;
>> return next json_build_object(first_sign_in, last_sign_in, ..rest of
>> details);
>> END LOOP
>>
>> but If I had 100 employees over a span of 30 days, this would be 6000
>> queries inside the loop! which I am sure you would agree is an overkill
>>
>>
>> is there a better way to do this?
>>
>>
>> Thanks.
>>
>>
>
>
> --
> Regards,
> Muhannad
>