Lets say I have a large table that just consists of three columns.
Integer id,
timestamp ts,
double value
If I wanted to get the values given a complicated date expression what is the best way to achieve that ?
For example if I wanted to get all the values at anytime on weekend days and only between 18:00 and 8:00 on weekdays and any time on school holidays for the year 2014.
Obviously some of these times are variable and so the solution should be dynamic. I was thinking
of storing a series of date intervals for things like school holidays in another table to check against. However, I would like to create a custom Postgres function to hide some of the complexity.
Does anyone know of similar code or have suggestions ?
Especially dealing with cases like the times above except on weekend logic ?
Thanks
With a holiday table
select *
from
t
left join
holiday on date_trunc('day', t.ts) = holiday.day
where
extract(dow from ts) in (0, 6) -- Weekend
or
(extract(hour from ts) >= 18 and extract(hour from ts) <= 8)
or
holiday.day is not null -- Holiday
Related
I am trying to ascertain a count of the couriers that are active every hour of a shift using the the start and end times of their shifts to create an array which I hope to group by. Firstly, when I run it I'm given epoch times back, secondly, I am not able to group by the hours array.
Does anyone have any solutions that they would kindly share with me?
**
SELECT
GENERATE_TIMESTAMP_ARRAY(CAST(fss.start_time_local AS TIMESTAMP), CAST(fss.end_time_local AS TIMESTAMP) , INTERVAL 1 hour) as hours,
#COUNT(sys_scheduled_shift_id) AS number_schedule_shift,
FROM just-data-warehouse.delco_analytics_team_dwh.fact_scheduled_shifts AS fss
#GROUP BY hours
**
For your reference the shift data for the courier is structured like so
To calculate how many couriers have been active at least one minute in every hour I would do it like this:
SELECT
CALENDAR.datetime
,SUM(workers.flag_worker) as n_workers
FROM (
-- CALENDAR
SELECT
cast(datetime as datetime) datetime
FROM UNNEST(GENERATE_TIMESTAMP_ARRAY('2022-01-01T00:00:00', '2022-01-02T00:00:00'
,INTERVAL 1 hour)) AS datetime
) CALENDAR
-- TABLE of SHIFTS
LEFT JOIN (
SELECT * , 1 flag_worker FROM
UNNEST(
ARRAY<STRUCT<worker_id string , shift_start datetime, shift_end datetime>>[
('Worker_01', '2022-01-01T06:00:00','2022-01-01T14:00:00')
,('Worker_02', '2022-01-01T10:00:00','2022-01-01T18:00:00')
]
)
AS workers
)workers
ON CALENDAR.datetime < workers.shift_end
AND DATETIME_ADD(CALENDAR.datetime, INTERVAL 1 hour) > workers.shift_start
GROUP BY CALENDAR.datetime
The idea is to build a calendar of datetimes and then join it with a table of shifts.
Instead of hours, the calendar can be modified to have fractions of hours. Also, there may be a more elegant way to build the calendar.
I need to round up a month-date based on certain parameters. For example: If I have a parameter where if a day in a given month is between the 6th and the 4th of the next month, I need my query to return the next months date. Is there a way to round up the month given these parameters without hard coding case whens for every single month ever?
SELECT case when date_trunc('day',li.created_at between '2019-03-06 00:00:00' and '2019-04-06 00:00:00' then '2019-04-01' end)
FROM line_items li
If you want the beginning of the month, but offset by 4 days, you can use date_trunc() and subtract some number of days (or add some number of days). You seem to want something like this:
select dateadd(month, 1, date_trunc('month', li.created_at - interval '4 day'))
Another approach is to create a canonical "dates" table that precomputes the mapping from a given date to a new date using your rounding scheme. The mapping could be done outside of redshift in a script and the table loaded in (or within redshift using a user defined function).
I'd like to figure out the age of a person based on two dates: their birthday and the date they were created in a database.
The age is being calculated in days instead of years, though. Here's my query:
SELECT date_of_birth as birthday, created_at, (created_at - date_of_birth) as Age
FROM public.users
WHERE date_of_birth IS NOT NULL
The date_of_birth field is a date w/o a timestamp, but the created_at field is a date with a timestamp (e.g. 2017-05-06 01:27:40).
And my output looks like this:
0 years 0 mons 9645 days 1 hours 27 mins 40.86485 secs
Any idea how can I round/calculate the ages by the nearest year?
Using PostgreSQL.
If you are using MS SQLServer than you could
CONVERT(DATE, created_at)
and than calculate difference in months like
DATEDIFF(month, created_at, GETDATE())/12
means you can use reminder in months to add or substract one year.
In PostgreSQL, dates are handled very differently to MSSQL & MySQL. In fact it follows the SQL standard very well, even if it’s not always intuitive.
To actually calculate the age of something, you can use age():
SELECT age(date1,date1)
Like all of PostgreSQL’s functions, there are variations of data type, and you may need to do something like this:
SELECT age(date1::date,date1::date)
or, more formally:
SELECT age(cast(date1 as date),cast(date1 as date))
The result will be an interval, which displays as a string :
SELECT age(current_date::date,'1981-01-17'::date);
-- 36 years 3 mons 22 days
If you just want the age in years, you can use extract:
SELECT extract('year' from age(current_date::date,'1981-01-17'::date));
Finally, if you want it correct to the nearest year, you can apply the old trick of adding half an interval:
extract('year' from age(current_date::date,'1981-01-17'::date)+interval '.5 year');
It’s not as simple as some of the other DBMS products, but it’s much more flexible, if you can get your head around it.
Here are some references:
https://www.postgresql.org/docs/current/static/functions-datetime.html
http://www.sqlines.com/postgresql/how-to/datediff
please help me with my problem. So, I have a table named 'RATES' which contains these columns:
id (int)
rate (money)
start_time (datetime)
end_time(datetime)
example data:
1 150 8:00am 6:00pm
2 200 6:00pm 4:00am
3 250 8:00am 4:00am (the next day)
What I have to do is to select all the id(s) to where a given time would fall.
e.g given time: 9:00 pm, the output should be 2,3
The problem is I got this time range between 8am to 4am the next day and I don't know what to do. Help, please! thanks in advance :D
Assuming that #Andriy M is correct:
Data never spans more than 24 hours
if end_time<=start_time then end_time belongs to the next day
then what you're looking for is this:
Declare #GivenTime DateTime
Set #GivenTime = '9:00 PM'
Select ID
From Rates
Where (Start_Time<End_Time And Start_Time<=#GivenTime And End_Time>=#GivenTime)
Or (Start_Time=End_Time And Start_Time=#GivenTime)
Or (Start_Time>End_Time And (Start_Time>=#GivenTime Or End_Time<=#GivenTime))
I don't really ever use MS SQL, but maybe this will help.
I was going to suggest something like this, but by the way you have your data set up, this would fail.
SELECT id FROM RATES
WHERE datepart(hh, start_time) <= 9 AND datepart(hh, end_time) >= 9;
You'll have you search using the actual date if you expect to get the correct data back.
SELECT id FROM RATES
WHERE start_time <= '2011-1-1 9:00' AND end_time >= '2011-1-1 9:00';
This may not be exactly correct, but it may help you look in the right direction.
I guess #gbn is not going to help you. I will try and fill in.
Given -- a table called timedata that has ranges only going over at most one day
WITH normalized AS
(
SELECT *
FROM timedata
WHERE datepart(day,start_time) = datepart(day,endtime)
UNION ALL
SELECT id, rate, start_time, dateadd(second,dateadd(day,datediff(day,0,end_time),0),-1) as end_time
FROM timedata
WHERE not (datepart(day,start_time) = datepart(day,endtime))
UNION ALL
SELECT id, rate,dateadd(day,datediff(day,0,end_time),0) as start_time, end_time
FROM timedata
WHERE not (datepart(day,start_time) = datepart(day,endtime))
)
SELECT *
FROM normalized
WHERE datepart(hour,start_time) < #inhour
AND datepart(hour,end_time) > #inhour
This makes use of a CTE and a trick to truncate datetime values. To understand this trick read this question and answer: Floor a date in SQL server
Here is an outline of what this query does:
Create a normalized table with each time span only going over one day by
Selecting all rows that occur on the same day.
Then for each entry that spans two days joining in
Selecting the starttime and one second before the next day as the end time for all that span.
and
Selecting 12am of the end_time date as the starttime and the end_time.
Finally you perform the select using the hour indicator on this normalized table.
If your ranges go over more than one day you would need to use a recursive CTE to get the same normalized table.
I am wanting to do some queries on a sales table and a purchases table, things like showing the total costs, or total sales of a particular item etc.
Both of these tables also have a date field, which stores dates in sortable format(just the default I suppose?)
I am wondering how I would do things with this date field as part of my query to use date ranges such as:
The last year, from any given date of the year
The last 30 days, from any given day
To show set months, such as January, Febuary etc.
Are these types of queries possible just using a DATE field, or would it be easier to store months and years as separate tex fields?
If a given DATE field MY_DATE, you can perform those 3 operation using various date functions:
1. Select last years records
SELECT * FROM MY_TABLE
WHERE YEAR(my_date) = YEAR(CURDATE()) - 1
2. Last 30 Days
SELECT * FROM MY_TABLE
WHERE DATE_SUB(CURDATE(), INTERVAL 30 DAY) < MY_DATE
3. Show the month name
SELECT MONTHNAME(MY_DATE), * FROM MY_TABLE
I have always found it advantageous to store dates as Unix timestamps. They're extremely easy to sort by and query by range, and MySQL has built-in features that help (like UNIX_TIMESTAMP() and FROM_UNIXTIME()).
You can store them in INT(11) columns; when you program with them you learn quickly that a day is 86400 seconds, and you can get more complex ranges by multiplying that by a number of days (e.g. a month is close enough to 86400 * 30, and programming languages usually have excellent facilities for converting to and from them built into standard libraries).