Re: Cross tabulations

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От Greg Stark
Тема Re: Cross tabulations
Дата
Msg-id 878ya128ya.fsf@stark.xeocode.com
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Ответ на Cross tabulations  ("Muhyiddin A.M Hayat" <middink@indo.net.id>)
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"Muhyiddin A.M Hayat" <middink@indo.net.id> writes:

> Dear all,
> 
> I need to do something similar to a cross tabulation, but without any
> aggregation.

join your table to itself four times:

select *  from (select check_time::date as date, employee_id, check_time-check_time::date as in from test where state =
'In')as a  join (select check_time::date as date, employee_id, check_time-check_time::date as break_out from test where
state= 'Break Out') as b using (employee_id,date) join (select check_time::date as date, employee_id,
check_time-check_time::dateas break_in from test where state = 'Break In') as d using (employee_id,date) join (select
check_time::dateas date, employee_id, check_time-check_time::date as out from test where state = 'Out') as e using
(employee_id,date);
 

Note that this will do strange things if you don't have precisely four records
for each employee.

Alternatively use subqueries:

select date, employee_id,      (select check_time-check_time::date from test where employee_id = x.employee_id and
check_time::date= date and state = 'In') as in,      (select check_time-check_time::date from test where employee_id =
x.employee_idand check_time::date = date and state = 'Break Out') as break_out,      (select
check_time-check_time::datefrom test where employee_id = x.employee_id and check_time::date = date and state = 'Break
In')as break_in,      (select check_time-check_time::date from test where employee_id = x.employee_id and
check_time::date= date and state = 'Out') as out from (select distinct employee_id, check_time::date as date from test)
asx; 
 

This will at least behave fine if there are missing records and will give an
error if there are multiple records instead of doing strange things.

Neither of these will be particularly pretty on the performance front.

-- 
greg



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