Re: [SQL] Please advice on query optimization - Mailing list pgsql-sql

Thanks folks for your help, I will benchmark the suggested solutions & see what's the best fit here.

Awesome mailing list :)

On Thu, Apr 20, 2017 at 11:37 PM, David G. Johnston <david.g.johnston@gmail.com> wrote:

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@gmail.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@reddoc.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@gmail.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

--

Regards,

Muhannad