I'm trying to generate a series in PostgreSQL with the generate_series function. I need a series of months starting from Jan 2008 until current month + 12 (a year out). I'm using and restricted to PostgreSQL 8.3.14 (so I don't have the timestamp series options in 8.4).
I know how to get a series of days like:
select generate_series(0,365) + date '2008-01-01'
But I am not sure how to do months.
select DATE '2008-01-01' + (interval '1' month * generate_series(0,11))
Edit
If you need to calculate the number dynamically, the following could help:
select DATE '2008-01-01' + (interval '1' month * generate_series(0,month_count::int))
from (
select extract(year from diff) * 12 + extract(month from diff) + 12 as month_count
from (
select age(current_timestamp, TIMESTAMP '2008-01-01 00:00:00') as diff
) td
) t
This calculates the number of months since 2008-01-01 and then adds 12 on top of it.
But I agree with Scott: you should put this into a set returning function, so that you can do something like select * from calc_months(DATE '2008-01-01')
You can interval generate_series like this:
SELECT date '2014-02-01' + interval '1' month * s.a AS date
FROM generate_series(0,3,1) AS s(a);
Which would result in:
date
---------------------
2014-02-01 00:00:00
2014-03-01 00:00:00
2014-04-01 00:00:00
2014-05-01 00:00:00
(4 rows)
You can also join in other tables this way:
SELECT date '2014-02-01' + interval '1' month * s.a AS date, t.date, t.id
FROM generate_series(0,3,1) AS s(a)
LEFT JOIN <other table> t ON t.date=date '2014-02-01' + interval '1' month * s.a;
You can interval generate_series like this:
SELECT TO_CHAR(months, 'YYYY-MM') AS "dateMonth"
FROM generate_series(
'2008-01-01' :: DATE,
'2008-06-01' :: DATE ,
'1 month'
) AS months
Which would result in:
dateMonth
-----------
2008-01
2008-02
2008-03
2008-04
2008-05
2008-06
(6 rows)
Well, if you only need months, you could do:
select extract(month from days)
from(
select generate_series(0,365) + date'2008-01-01' as days
)dates
group by 1
order by 1;
and just parse that into a date string...
But since you know you'll end up with months 1,2,..,12, why not just go with select generate_series(1,12);?
In the generated_series() you can define the step, which is one month in your case. So, dynamically you can define the starting date (i.e. 2008-01-01), the ending date (i.e. 2008-01-01 + 12 months) and the step (i.e. 1 month).
SELECT generate_series('2008-01-01', '2008-01-01'::date + interval '12 month', '1 month')::date AS generated_dates
and you get
1/1/2008
2/1/2008
3/1/2008
4/1/2008
5/1/2008
6/1/2008
7/1/2008
8/1/2008
9/1/2008
10/1/2008
11/1/2008
12/1/2008
1/1/2009
Related
i want the year intervals like this
fromdate = 15-09-2019, todate=21-09-2021
15-09-2019 - 31-12-2019 //for the year 2019
01-01-2020 - 31-12-2020 //for the year 2020
01-01-2021 - 21-12-2021 //for the year 2021
so that i can able to get data from those intervals
In this table i have values only for 2021 but not for 2019 and 2020
If any there is no data in the range of 2019 and 2020.It should prdouce 0 for the parameter Traincount and tonnage.
Simply subtract them:
SELECT ('2015-01-12'::date - '2015-01-01'::date) AS days;
The result:
days
------
11
There is a brute force approach to getting a yearly summary, which is to break the data out by days and then aggregate:
select min(dte), max(dte)
from generate_series('2019-09-15'::date, '2021-09-21'::date, interval '1 day') gs(dte)
group by date_trunc('year', dte);
However, more efficient method would avoid aggregation:
select greatest(gs.dte, v.fromdate),
least(gs.dte + interval '1 year - 1 day', v.todate)
from (values ('2019-09-15'::date, '2021-09-21'::date)) v(fromdate, todate) cross join lateral
generate_series(date_trunc('year', v.fromdate), date_trunc('year', v.todate), interval '1 year') gs(dte);
Here is a db<>fiddle.
You can try
select extract('year' from now()) - extract('year' from now());
I have a query that can create a table with dates like below:
with digit as (
select 0 as d union all
select 1 union all select 2 union all select 3 union all
select 4 union all select 5 union all select 6 union all
select 7 union all select 8 union all select 9
),
seq as (
select a.d + (10 * b.d) + (100 * c.d) + (1000 * d.d) as num
from digit a
cross join
digit b
cross join
digit c
cross join
digit d
order by 1
)
select (last_day(sysdate)::date - seq.num)::date as "Date"
from seq;
How could this be changed to generate only dates
Thanks
demo:db<>fiddle
WITH dates AS (
SELECT
date_trunc('month', CURRENT_DATE) AS first_day_of_month,
date_trunc('month', CURRENT_DATE) + interval '1 month -1 day' AS last_day_of_month
)
SELECT
generate_series(first_day_of_month, last_day_of_month, interval '1 day')::date
FROM dates
date_trunc() truncates a type date (or timestamp) to a certain date part. date_trunc('month', ...) removes all parts but year and month. All other parts are set to their lowest possible values. So, the day part is set to 1. That's why you get the first day of month with this.
adding a month returns the first of the next month, subtracting a day from this results in the last day of the current month.
Finally you can generate a date series with start and end date using the generate_series() function
Edit: Redshift does not support generate_series() with type date and timestamp but with integer. So, we need to create an integer series instead and adding the results to the first of the month:
db<>fiddle
WITH dates AS (
SELECT
date_trunc('month', CURRENT_DATE) AS first_day_of_month,
date_trunc('month', CURRENT_DATE) + interval '1 month -1 day' AS last_day_of_month
)
SELECT
first_day_of_month::date + gs
FROM
dates,
generate_series(
date_part('day', first_day_of_month)::int - 1,
date_part('day', last_day_of_month)::int - 1
) as gs
This answers the original version of the question.
You would use generate_series():
select gs.dte
from generate_series(date_trunc('month', now()::date),
date_trunc('month', now()::date) + interval '1 month' - interval '1 day',
interval '1 day'
) gs(dte);
Here is a db<>fiddle.
In a Postgres 9.1 database, I am trying to generate a series of weeks for a given month but with some constraints. I need all weeks to start on Monday and get cut when they start or end in another month.
Example:
For February, 2013 I want to generate a series like this:
start
------------------------
2013-02-01 00:00:00+00
2013-02-04 00:00:00+00
2013-02-11 00:00:00+00
2013-02-18 00:00:00+00
2013-02-25 00:00:00+00
The query that I have now looks like this:
SELECT GREATEST(date_trunc('week', dates.d),
date_trunc('month',dates.d)) as start
FROM generate_series(to_timestamp(1359676800),to_timestamp(1362095999), '1 week') as dates(d)
This query gets me the first 4 weeks but it's missing the week from the 25th. Is it possible to get the last week?
SELECT generate_series(date_trunc('week', date '2013-02-01' + interval '6 days')
, date_trunc('week', date '2013-02-01' + interval '1 month - 1 day')
, interval '1 week')::date AS day
UNION SELECT date '2013-02-01'
ORDER BY 1;
This variant does not need a subselect, GREATEST or GROUP BY and only generates the required rows. Simpler, faster. It's cheaper to UNION one row.
Add 6 days to the first day of the month before date_trunc('week', ...) to compute the first Monday of the month.
Add 1 month and subtract 1 day before date_trunc('week', ...) to get the last Monday of the month.
This can conveniently be stuffed into a single interval expression: '1 month - 1 day'
UNION (not UNION ALL) the first day of the month to add it unless it's already included as Monday.
Note that date + interval results in timestamp, which is the optimum here. Detailed explanation:
Generating time series between two dates in PostgreSQL
Automation
You can provide the start of the date series in a CTE:
WITH t(d) AS (SELECT date '2013-02-01') -- enter 1st of month once
SELECT generate_series(date_trunc('week', d + interval '6 days')
, date_trunc('week', d + interval '1 month - 1 day')
, interval '1 week')::date AS day
FROM t
UNION SELECT d FROM t
ORDER BY 1;
Or wrap it into a simple SQL function for convenience with repeated calls:
CREATE OR REPLACE FUNCTION f_week_starts_this_month(date)
RETURNS SETOF date AS
$func$
SELECT generate_series(date_trunc('week', $1 + interval '6 days')
, date_trunc('week', $1 + interval '1 month - 1 day')
, interval '1 week')::date AS day
UNION
SELECT $1
ORDER BY 1
$func$ LANGUAGE sql IMMUTABLE;
Call:
SELECT * FROM f_week_starts_this_month('2013-02-01');
You would pass the date for the first day of the month, but it works for any date. You the first day and all Mondays for the following month.
select
greatest(date_trunc('week', dates.d), date_trunc('month',dates.d)) as start
from generate_series('2013-02-01'::date, '2013-02-28', '1 day') as dates(d)
group by 1
order by 1
I've been working on this for a few hours with no luck and have hit a wall. My data looks like this:
Date1 Date2
2012-05-06 2012-05-05
2012-03-20 2012-01-05
What I'm trying to do is add 1 to the count for every month between two dates. So my output would ideally look like this:
Year Month Sum
2012 2 1
In other words, it should check for "empty" months between two dates and add 1 to them.
This is the code I've worked out so far. It will basically count the number of months between the two dates and group them into months and years.
SELECT
EXTRACT(YEAR FROM Date2::date) as "Year",
EXTRACT(MONTH FROM Date2::date) as "Month",
SUM(DATE_PART('year', Date1::date) - DATE_PART('year', Date2::date)) * 12 +
(DATE_PART('month', Date1::date) - DATE_PART('month', Date2::date))
FROM
test
GROUP BY
"Year",
"Month",
ORDER BY
"Year" DESC,
"Month" DESC;
This is where I'm stuck - I don't know how to actually add 1 for each of the "empty" months.
Test setup
With some sample rows (should be provided in the question):
CREATE TABLE test (
test_id serial PRIMARY KEY
, date1 date NOT NULL
, date2 date NOT NULL
);
INSERT INTO test(date1, date2)
VALUES
('2012-03-20', '2012-01-05') -- 2012-02 lies in between
, ('2012-01-20', '2012-03-05') -- 2012-02 (reversed)
, ('2012-05-06', '2012-05-05') -- nothing
, ('2012-05-01', '2012-06-30') -- still nothing
, ('2012-08-20', '2012-11-05') -- 2012-09 - 2012-10
, ('2012-11-20', '2013-03-05') -- 2012-12 - 2013-02
;
Postgres 9.3 or newer
Use a LATERAL join:
SELECT to_char(mon, 'YYYY') AS year
, to_char(mon, 'MM') AS month
, count(*) AS ct
FROM (
SELECT date_trunc('mon', least(date1, date2)::timestamp) + interval '1 mon' AS d1
, date_trunc('mon', greatest(date1, date2)::timestamp) - interval '1 mon' AS d2
FROM test
) sub1
, generate_series(d1, d2, interval '1 month') mon -- implicit CROSS JOIN LATERAL
WHERE d2 >= d1 -- exclude ranges without gap right away
GROUP BY mon
ORDER BY mon;
What is the difference between LATERAL and a subquery in PostgreSQL?
Postgres 9.2 or older
No LATERAL, yet. Use a subquery instead:
SELECT to_char(mon, 'YYYY') AS year
, to_char(mon, 'MM') AS month
, count(*) AS ct
FROM (
SELECT generate_series(d1, d2, interval '1 month') AS mon
FROM (
SELECT date_trunc('mon', least(date1, date2)::timestamp) + interval '1 mon' AS d1
, date_trunc('mon', greatest(date1, date2)::timestamp) - interval '1 mon' AS d2
FROM test
) sub1
WHERE d2 >= d1 -- exclude ranges without gap right away
) sub2
GROUP BY mon
ORDER BY mon;
Result
year | month | ct
------+-------+----
2012 | 2 | 2
2012 | 9 | 1
2012 | 10 | 1
2012 | 12 | 1
2013 | 1 | 1
2013 | 2 | 1
db<>fiddle here
SQL Fiddle.
Explanation
You are looking for complete calendar months between the two dates.
These queries work with any dates or timestamps in ascending or descending order and should perform well.
The WHERE clause is optional, since generate_series() returns no row if start > end. But it should be a bit faster to exclude empty ranges a priori.
The cast to timestamp makes it a bit cleaner and faster. Rationale:
Generating time series between two dates in PostgreSQL
AFAIK you can simply substract/add dates in postgresql
'2001-06-27 14:43:21'::DATETIME - '2001-06-27 14:33:21'::DATETIME = '00:10:00'::INTERVAL
So in your case that request part should look like
DATE_PART('month', Date1::datetime - Date2::datetime) as "MonthInterval"
age(timestamp1, timestamp2) => returns interval
the we try to extract year and month out of the interval and add them accordingly.
select extract(year from age(timestamp1, timestamp2))*12 + extract(month from
age(timestamp1, timestamp2))
I have a table in a PostgreSQL database containing dates and a total count per day.
mydate total
2012-05-12 12
2012-05-14 8
2012-05-13 4
2012-05-12 12
2012-05-15 2
2012-05-17 1
2012-05-18 1
2012-05-21 1
2012-05-25 1
Now I need to get the weekly totals for a given date range.
Ex. I want to get the weekly totals from 2012-05-01 up to 2012-05-31.
I'm looking at this output:
2012-05-01 2012-05-07 0
2012-05-08 2012-05-14 36
2012-05-15 2012-05-22 5
2012-05-23 2012-05-29 1
2012-05-30 2012-05-31 0
This works for any given date range:
CREATE FUNCTION f_tbl_weekly_sumtotals(_range_start date, _range_end date)
RETURNS TABLE (week_start date, week_end date, sum_total bigint)
LANGUAGE sql AS
$func$
SELECT w.week_start, w.week_end, COALESCE(sum(t.total), 0)
FROM (
SELECT week_start::date, LEAST(week_start::date + 6, _range_end) AS week_end
FROM generate_series(_range_start::timestamp
, _range_end::timestamp
, interval '1 week') week_start
) w
LEFT JOIN tbl t ON t.mydate BETWEEN w.week_start and w.week_end
GROUP BY w.week_start, w.week_end
ORDER BY w.week_start
$func$;
Call:
SELECT * FROM f_tbl_weekly_sumtotals('2012-05-01', '2012-05-31');
Major points
I wrapped it in a function for convenience, so the date range has to be provided once only.
The subquery w produces the series of weeks starting from the first day of the given date range. The upper bound is capped with LEAST to stay within the upper bound of the given date range.
Then LEFT JOIN to the data table (tbl in my example) to keep all weeks in the result, even where no data rows are found.
The rest should be obvious. COALESCE to output 0 instead of NULL for empty weeks.
Data types have to match, I assumed mydate date and total int for lack of information. (The sum() of an int is bigint.)
Explanation for my particular use of generate_series():
Generating time series between two dates in PostgreSQL
Using this function
CREATE OR REPLACE FUNCTION last_day(date)
RETURNS date AS
$$
SELECT (date_trunc('MONTH', $1) + INTERVAL '1 MONTH - 1 day')::date;
$$ LANGUAGE 'sql' IMMUTABLE STRICT;
AND generate_series (from 8.4 onwards) we can create the date partitions.
SELECT wk.wk_start,
CAST(
CASE (extract(month from wk.wk_start) = extract(month from wk.wk_start + interval '6 days'))
WHEN true THEN wk.wk_start + interval '6 days'
ELSE last_day(wk.wk_start)
END
AS date) AS wk_end
FROM
(SELECT CAST(generate_series('2012-05-01'::date,'2012-05-31'::date,interval '1 week') AS date) AS wk_start) AS wk;
Then putting it together with the data
CREATE TABLE my_tab(mydate date,total integer);
INSERT INTO my_tab
values
('2012-05-12'::date,12),
('2012-05-14'::date,8),
('2012-05-13'::date,4),
('2012-05-12'::date,12),
('2012-05-15'::date,2),
('2012-05-17'::date,1),
('2012-05-18'::date,1),
('2012-05-21'::date,1),
('2012-05-25'::date,1);
WITH month_by_week AS
(SELECT wk.wk_start,
CAST(
CASE (extract(month from wk.wk_start) = extract(month from wk.wk_start + interval '6 days'))
WHEN true THEN wk.wk_start + interval '6 days'
ELSE last_day(wk.wk_start)
END
AS date) AS wk_end
FROM
(SELECT CAST(generate_series('2012-05-01'::date,'2012-05-31'::date,interval '1 week') AS date) AS wk_start) AS wk
)
SELECT month_by_week.wk_start,
month_by_week.wk_end,
SUM(COALESCE(mt.total,0))
FROM month_by_week
LEFT JOIN my_tab mt ON mt.mydate BETWEEN month_by_week.wk_start AND month_by_week.wk_end
GROUP BY month_by_week.wk_start,
month_by_week.wk_end
ORDER BY month_by_week.wk_start;