Hi I have a entrytime and exittime timestamp in my database, how can I query it to display only ones where the person exited more than an hour later;
Select * from store where EXTRACT(EPOCH FROM (exittime - entrytime))/3600 >60
That's what I have so far but it won't work, any help would be appreciated.
Just subtract the values and compare it with an interval
Select *
from store
where exittime - entrytime > interval '1 hour';
This assumes that both columns are defined as timestamptz or timestamp
I’m building a booking system where a user will set their availability eg: I’m available Monday’s from 9am to 11am, Tuesdays from 9am to 5pm etc… and need to generate a list of time slots 15mins apart from their availability.
I have the following table (but am flexible to changing this):
availabilities(day_of_week text, start_time: time, end_time: time)
which returns records like:
‘Monday’ | 09:00:00 | 11:00:00
‘Monday’ | 13:00:00 | 17:00:00
‘Tuesday’ | 08:00:00 | 17:00:00
So I’m trying to build a stored procedure to generate a list of time slots so far I've got this:
create or replace function timeslots ()
return setof timeslots as $$
declare
rec record;
begin
for rec in select * from availabilities loop
/*
convert 'Monday' | 09:00:00 | 11:00:00 into:
2020-02-03 09:00:00
2020-02-03 09:15:00
2020-02-03 09:30:00
2020-02-03 09:45:00
2020-02-03 10:00:00
and so on...
*/
return next
end loop
$$ language plpgsql stable;
I return a setof instead of a table as I'm using Hasura and it needs to return a setof so I just create a blank table.
I think I'm on the right track but am currently stuck on:
how do I create a timestamp from 'Monday' 09:00:00 for the next monday as I only care about timeslots from today onwards?
how do I convert 'Monday' | 09:00:00 | 11:00:00 into a list of time slots 15 mins apart?
how do I create a timestamp from 'Monday' 09:00:00 for the next monday
as I only care about timeslots from today onwards?
You can use date_trunc for this (see this question for more info):
SELECT date_trunc('week', current_date) + interval '1 week';
From the docs re week:
The number of the ISO 8601 week-numbering week of the year. By
definition, ISO weeks start on Mondays
So taking this value and adding a week gives next Monday (you may need to ammend this behaviour based upon what you want to do if today is monday!).
how do I convert 'Monday' | 09:00:00 | 11:00:00 into a list of time
slots 15 mins apart?
This is a little tricker; generate_series will give you the timeslots but the trick is getting it into a result set. The following should do the job (I have included your sample data; change the values bit to refer to your table) - dbfiddle :
with avail_times as (
select
date_trunc('week', current_date) + interval '1 week' + case day_of_week when 'Monday' then interval '0 day' when 'Tuesday' then interval '1 day' end + start_time as start_time,
date_trunc('week', current_date) + interval '1 week' + case day_of_week when 'Monday' then interval '0 day' when 'Tuesday' then interval '1 day' end + end_time as end_time
from
(
values
('Monday','09:00:00'::time,'11:00:00'::time),
('Monday','13:00:00'::time,'17:00:00'::time),
('Tuesday','08:00:00'::time,'17:00:00'::time)
) as availabilities (day_of_week,
start_time,
end_time) )
select
g.ts
from
(
select
start_time,
end_time
from
avail_times) avail,
generate_series(avail.start_time, avail.end_time - interval '1ms', '15 minutes') g(ts);
A few notes:
The CTE avail_times is used to simplify things; it generates two columns (start_time and end_time) which are the full timestamps (so including the date). In this example the first row is "2020-02-03 09:00:00, 2020-02-03 11:00:00" (I'm running this on 2020-02-02 so 2020-02-03 is next Monday).
The way I'm converting 'monday' etc to a day of the week is a bit of a hack (and I have not bothered to do the full week); there is probably a better way but storing the day of week as an integer would make this simpler.
I subtract 1ms from the end time because I'm assuming you dont want this in the result set.
The main query is using a LATERAL Subquery. See this question for more info.
Aditional Question
how to adjust this so I can pass in a start and end date so I can get
time slots for a particular period
You could do something like the following (just adjust the dates CTE to return whatever days you want to include; you could convert to a function or just pass the dates in as parameters).
Note that as #Belayer mentions my original solution did not cater for shifts over midnight so this addresses that too.
with dates as (
select
day
from
generate_series('2020-02-20'::date, '2020-03-10'::date, '1 day') as day ),
availabilities as (
select
*
from
(
values (1,'09:00:00'::time,'11:00:00'::time),
(1,'13:00:00'::time,'17:00:00'::time),
(2,'08:00:00'::time,'17:00:00'::time),
(3,'23:00:00'::time,'01:00:00'::time)
) as availabilities
(day_of_week, -- 1 = monday
start_time,
end_time) ) ,
avail_times as (
select
d.day + start_time as start_time,
case
end_time > start_time
when true then d.day
else d.day + interval '1 day' end + end_time as end_time
from
availabilities a
inner join dates d on extract(ISODOW from d.day) = a.day_of_week )
select
g.ts
from
(
select
start_time,
end_time
from
avail_times) avail,
generate_series(avail.start_time, avail.end_time - interval '1ms', '15 minutes') g(ts)
order by
g.ts;
The following uses much of the techniques mentioned by #Brits. They present some very good information, so I'll not repeat but suggest you review it (and the links).
I do however take a slightly different approach. First a couple table changes. I use the ISO day of week 1-7 (Monday-Sunday) rather than the day name. The day name is easily extracted for the dater later.
Also I use interval instead to time for start and end times. ( A time data type works for most scenarios but there is one it doesn't (more later).
One thing your description does not make clear is whether the ending time is included it the available time or not. If included the last interval would be 11:00-11:15. If excluded the last interval is 10:45-11:00. I have assumed to excluded it. In the final results the end time is to be read as "up to but not including".
-- setup
create table availabilities (weekday integer, start_time interval, end_time interval);
insert into availabilities (weekday , start_time , end_time )
select wkday
, start_time
, end_time
from (select *
from (values (1, '09:00'::interval, '11:00'::interval)
, (1, '13:00'::interval, '17:00'::interval)
, (2, '08:00'::interval, '17:00'::interval)
, (3, '08:30'::interval, '10:45'::interval)
, (4, '10:30'::interval, '12:45'::interval)
) as v(wkday,start_time,end_time)
) r ;
select * from availabilities;
The Query
It begins with a CTE (next_week) generates a entry for each day of the week beginning Monday and the appropriate ISO day number for it. The main query joins these with the availabilities table to pick up times for matching days. Finally that result is cross joined with a generated timestamp to get the 15 minute intervals.
-- Main
with next_week (wkday,tm) as
(SELECT n+1, date_trunc('week', current_date) + interval '1 week' + n*interval '1 day'
from generate_series (0, 6) n
)
select to_char(gdtm,'Day'), gdtm start_time, gdtm+interval '15 min' end_time
from ( select wkday, tm, start_time, end_time
from next_week nw
join availabilities av
on (av.weekday = nw.wkday)
) s
cross join lateral
generate_series(start_time+tm, end_time+tm- interval '1 sec', interval '15 min') gdtm ;
The outlier
As mentioned there is one scenario where a time data type does not work satisfactory, but you may not nee it. What happens when a shift worker says they available time is 23:00-01:30. Believe me when a shift worker goes to work at 22:00 of Friday, 01:30 is still Friday night, even though the calendar might not agree. (I worked that shift for many years.) The following using interval handles that issue. Loading the same data as prior with an addition for the this case.
insert into availabilities (weekday, start_time, end_time )
select wkday
, start_time
, end_time + case when end_time < start_time
then interval '1 day'
else interval '0 day'
end
from (select *
from (values (1, '09:00'::interval, '11:00'::interval)
, (1, '13:00'::interval, '17:00'::interval)
, (2, '08:00'::interval, '17:00'::interval)
, (3, '08:30'::interval, '10:45'::interval)
, (5, '23:30'::interval, '02:30'::interval) -- Friday Night - Saturday Morning
) as v(wkday,start_time,end_time)
) r
;
select * from availabilities;
Hope this helps.
I need to truncate dates to the start of week, which is Sunday in my case. How can I do this in PostgreSQL? This truncates to Monday:
date_trunc('week', mydate)
If you subtract the dow value (0 for Sundays, 6 for Saturdays) from the current date than you get the previous Sunday which is the begin of your Sunday-based week
demo:db<>fiddle
SELECT
my_date - date_part('dow', my_date)::int
FROM
my_table
Further reading, documentation
You could truncate the date to the week's Monday, then subtract 1 day, e.g:
SELECT (date_trunc('week', now() + interval '1 day') - interval '1 day')::DATE;
date
------------
2019-06-16
As per documentation, date_trunc() accepts values of type date and timestamp and returns a timestamp (thus the cast at the end).
I have a table in my postgres database which has a column of dates. I want to search which of those dates is missing - for example:
date
2016-11-09 18:30:00
2016-11-09 19:00:00
2016-11-09 20:15:00
2016-11-09 22:20:00
2016-11-09 23:00:00
Here, |2016-11-09 21:00:00| is missing. After sorting my generated series if my table has an entry between two slots (slot of 1 hr interval) i need to remove that.
I want to make a query with generate_series that returns me the date which is missing. Is this possible?.
sample query that i used to generate series.
SELECT t
FROM generate_series(
TIMESTAMP WITH TIME ZONE '2016-11-09 18:00:00',
TIMESTAMP WITH TIME ZONE '2016-11-09 23:00:00',
INTERVAL '1 hour'
) t
EXCEPT
SELECT tscol
FROM mytable;
But this query is not removing 2016-11-09 18:30:00,2016-11-09 20:15:00 etc. cuz i used except.
This is not a gaps-and-island problem. You just want to find the 1 hour intervals for which no record exist in the table.
EXCEPT does not work here because it does equality comparison, while you want to check if a record exists or not within a range.
A typical solution for this is to use a left join antipattern:
select dt
from generate_series(
timestamp with time zone '2016-11-09 18:00:00',
timestamp with time zone '2016-11-09 23:00:00',
interval '1 hour'
) d(dt)
left join mytable t
on t.tscol >= dt and t.tscol < dt + interval '1 hour'
where t.tscol is null
You can also use not exists:
select dt
from generate_series(
timestamp with time zone '2016-11-09 18:00:00',
timestamp with time zone '2016-11-09 23:00:00',
interval '1 hour'
) d(dt)
where not exists (
select 1
from mytable t
where t.tscol >= dt and t.tscol < dt + interval '1 hour'
)
In this demo on DB Fiddle, both queries return:
| dt |
| :--------------------- |
| 2016-11-09 21:00:00+00 |
I want to get last 24 hrs data. i wrote a query in postgreSQL as follows. But I couldn't get the answer as i expected.
SELECT startdate::timestamp AS startdate,
(DATE_PART('hour',startdate::timestamp)::integer) as hrs,count(guorderid)
FROM ord_entitlement
WHERE DATE_PART('Day',CURRENT_DATE::timestamp - startdate::timestamp) < 1
AND DATE_PART('hour',startdate::timestamp) <= 24
GROUP BY hrs,startdate
ORDER BY startdate
Instead of checking date parts, do the time math to get an interval. Use NOW() to get a timestamptz.
SELECT startdate::timestamp AS startdate,
(DATE_PART('hour',startdate::timestamp)::integer) as hrs,
count(guorderid)
FROM ord_entitlement
WHERE NOW() > startdate::timestamptz
AND NOW() - startdate::timestamptz <= interval '24 hours'
GROUP BY hrs,startdate
ORDER BY startdate
This ensures you will get the last 24 hours no matter what your time zone or daylight savings says. NOW() > startdate::timestamptz ensures you don't accidentally pick up things from the future.
If you use CURRENT_DATE you will not get the time instead use now() function. Try the following,
SELECT startdate::timestamp AS startdate,
(DATE_PART('hour',startdate::timestamp)::integer) as hrs,count(guorderid)
FROM ord_entitlement
WHERE DATE_PART('Day',now() - startdate::timestamptz) < 1
GROUP BY hrs,startdate
ORDER BY startdate
date_part() works like extract(), i.e. they will extract a subfield from the source:
-- they will both yield 9 as result
select date_part('day', date '2015-01-09') "day part of 2015-01-09",
date_part('day', date '2015-02-09') "day part of 2015-02-09";
Extracting day(s) therefore is not suited to select the last 24 hours. Similarly extracting hour(s) will (almost) always yield less than or equal to 24.
Extraction day(s) from interval (that's the result of substracting 2 timestamps) is a little different. The result might depend on, whether the interval is justified, or not:
-- they will both yield 1 as result
select date_part('day', interval '1 day') "day part of 1 day",
date_part('day', interval '1 month 1 day') "day part of 1 month 1 day";
-- they will yield 1, 32 and 397 respectively
select date_part('day', timestamp '2015-02-09' - timestamp '2015-02-08') "interval 1",
date_part('day', timestamp '2015-02-09' - timestamp '2015-01-08') "interval 2",
date_part('day', timestamp '2015-02-09' - timestamp '2014-01-08') "interval 3";
Depending on the fact, that the timestamp subtraction is not giving justified intervals is not the best option, I think. You could use simpler conditions to achieve your goal:
-- if startdate is a timestamp:
where current_timestamp - interval '1 day' <= startdate
-- if startdate is a date:
where current_date - 1 <= startdate
If you want to disallow future dates too (as your question's title suggests), you could use a single between condition:
-- if startdate is a timestamp:
where startdate between current_timestamp - interval '1 day' and current_timestamp
-- if startdate is a date:
where startdate between current_date - 1 and current_date