Is there a way to create a date column combining one column having the year as string and one column containing a date-of-year (doy) as integer?
I am aware of methods like SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); or SELECT to_char(date_trunc('year', now()) + interval '169 days', 'MM/DD') but when trying to replace the "hard coded" stings with the columns I always get some kind of an error.
SELECT s.id, s.year, s.doy,
((s.year||'-01-01')::date + (s.doy||' days')::interval )::date AS date
FROM table_name AS s
the (s.year||'-01-01') or (s.doy||' days') concats the column value with a required string and the ::date or ::interval changes the resulting string type
You can use the make_date() function and add the number of days directly because date + integer is a valid operation:
select make_date(s.year, 1, 1) + s.doy as date
from ...
I have a table x(x_id, ts), where ts is a timestamp.
And I have a second table y(y_id, day, month, year), which is supposed to have its values from x(ts).
(Both x_id and y_id are serial)
For example:
x y
_x_id_|__________ts__________ _y_id_|_day_|_month_|__year__
1 | '2019-10-17 09:10:08' 1 17 10 2019
2 | '2019-01-26 11:12:02' 2 26 1 2019
However, if on x I have 2 timestamps on the same day but different hour, this how both tables should look like:
x y
_x_id_|__________ts__________ _y_id_|_day_|_month_|__year__
1 | '2019-10-17 09:10:08' 1 17 10 2019
2 | '2019-10-17 11:12:02'
Meaning y can't have 2 rows with the same day, month and year.
Currently, the way I'm doing this is:
INSERT INTO y(day, month, year)
SELECT
EXTRACT(day FROM ts) AS day,
EXTRACT(month FROM ts) AS month,
EXTRACT(year FROM ts) AS year
FROM x
ORDER BY year, month, day;
However, as you probably know, this doesn't check if the timestamps share the same date, so how can I do that?
Thank you for your time!
Assuming you build the unique index as recommended above change your insert to:
insert into y(day, month, year)
select extract(day from ts) as day,
, extract(month from ts) as month,
, extract(year from ts) as year
from x
on conflict do nothing;
I hope your table X is not very large as the above insert (like your original) will attempt inserting a row into Y for every row in X on every execution - NO WHERE clause.
Add a UNIQUE constraint on table y to prevent adding the same date twice.
CREATE UNIQUE INDEX CONCURRENTLY y_date
ON y (year,month,day)
Then add it to y:
ALTER TABLE y
ADD CONSTRAINT y_unique_date
UNIQUE USING INDEX y_date
Note that you'll get an SQL error when the constraint is violated. If you don't want that and just ignore the INSERT, use a BEFORE INSERT trigger, returning NULL when you detect the "date" already exists, or just use ON CONFLICT DO NOTHING in your INSERT statement, as hinted by #Belayer.
I am creating a Customer table and i want one of the attributes to be Expiry Date of credit card.I want the format to be 'Month Year'. What data type should i use? i want to use date but the format is year/month/day. Is there any other way to restrict format to only Month and year?
You can constrain the date to the first day of the month:
create table customer (
cc_expire date check (cc_expire = date_trunc('month', cc_expire))
);
Now this fails:
insert into customer (cc_expire) values ('2014-12-02');
ERROR: new row for relation "customer" violates check constraint "customer_cc_expire_check"
DETAIL: Failing row contains (2014-12-02).
And this works:
insert into customer (cc_expire) values ('2014-12-01');
INSERT 0 1
But it does not matter what day is entered. You will only check the month:
select
date_trunc('month', cc_expire) > current_date as valid
from customer;
valid
-------
t
Extract year and month separately:
select extract(year from cc_expire) "year", extract(month from cc_expire) "month"
from customer
;
year | month
------+-------
2014 | 12
Or concatenated:
select to_char(cc_expire, 'YYYYMM') "month"
from customer
;
month
--------
201412
Use either
char(5) for two-digit years, or
char(7) for four-digit years.
Code below assumes two-digit years, which is the form that matches all my credit cards. First, let's create a table of valid expiration dates.
create table valid_expiration_dates (
exp_date char(5) primary key
);
Now let's populate it. This code is just for 2013. You can easily adjust the range by changing the starting date (currently '2013-01-01'), and the "number" of months (currently 11, which lets you get all of 2013 by adding from 0 to 11 months to the starting date).
with all_months as (
select '2013-01-01'::date + (n || ' months')::interval months
from generate_series(0, 11) n
)
insert into valid_expiration_dates
select to_char(months, 'MM') || '/' || to_char(months, 'YY') exp_date
from all_months;
Now, in your data table, create a char(5) column, and set a foreign key reference from it to valid_expiration_dates.exp_date.
While you're busy with this, think hard about whether "exp_month" might be a better name for that column than "exp_date". (I think it would.)
As another idea you could essentially create some brief utilities to do this for you using int[]:
CREATE OR REPLACE FUNCTION exp_valid(int[]) returns bool LANGUAGE SQL IMMUTABLE as
$$
SELECT $1[1] <= 12 AND (select count(*) = 2 FROM unnest($1));
$$;
CREATE OR REPLACE FUNCTION first_invalid_day(int[]) RETURNS date LANGUAGE SQL IMMUTABLE AS
$$
SELECT (to_date($1[2]::text || $1[1]::text, CASE WHEN $1[2] < 100 THEN 'YYMM' ELSE 'YYYYMM' END) + '1 month'::interval)::date;
$$;
These work:
postgres=# select exp_valid('{04,13}');
exp_valid
-----------
t
(1 row)
postgres=# select exp_valid('{13,04}');
exp_valid
-----------
f
(1 row)
postgres=# select exp_valid('{04,13,12}');
exp_valid
-----------
f
(1 row)
Then we can convert these into a date:
postgres=# select first_invalid_day('{04,13}');
first_invalid_day
-------------------
2013-05-01
(1 row)
This use of arrays does not violate any normalization rules because the array as a whole represents a single value in its domain. We are storing two integers representing a single date. '{12,2}' is December of 2002, while '{2,12}' is Feb of 2012. Each represents a single value of the domain and is therefore perfectly atomic.
I work with a Postgres database. This DB has a table with users, who have a birthdate (date field). Now I want to get all users who have their birthday in the upcoming week....
My first attempt: SELECT id FROM public.users WHERE id IN (lange reeks) AND birthdate > NOW() AND birthdate < NOW() + interval '1 week'
But this does not result, obviously because off the year. How can I work around this problem?
And does anyone know what happen to PG would go with the cases at 29-02 birthday?
We can use a postgres function to do this in a really nice way.
Assuming we have a table people, with a date of birth in the column dob, which is a date, we can create a function that will allow us to index this column ignoring the year. (Thanks to Zoltán Böszörményi):
CREATE OR REPLACE FUNCTION indexable_month_day(date) RETURNS TEXT as $BODY$
SELECT to_char($1, 'MM-DD');
$BODY$ language 'sql' IMMUTABLE STRICT;
CREATE INDEX person_birthday_idx ON people (indexable_month_day(dob));
Now, we need to query against the table, and the index. For instance, to get everyone who has a birthday in April of any year:
SELECT * FROM people
WHERE
indexable_month_day(dob) >= '04-01'
AND
indexable_month_day(dob) < '05-01';
There is one gotcha: if our start/finish period crosses over a year boundary, we need to change the query:
SELECT * FROM people
WHERE
indexable_month_day(dob) >= '12-29'
OR
indexable_month_day(dob) < '01-04';
To make sure we match leap-day birthdays, we need to know if we will 'move' them a day forward or backwards. In my case, it was simpler to just match on both days, so my general query looks like:
SELECT * FROM people
WHERE
indexable_month_day(dob) > '%(start)%'
%(AND|OR)%
indexable_month_day(dob) < '%(finish)%';
I have a django queryset method that makes this all much simpler:
def birthday_between(self, start, finish):
"""Return the members of this queryset whose birthdays
lie on or between start and finish."""
start = start - datetime.timedelta(1)
finish = finish + datetime.timedelta(1)
return self.extra(where=["indexable_month_day(dob) < '%(finish)s' %(andor)s indexable_month_day(dob) > %(start)s" % {
'start': start.strftime('%m-%d'),
'finish': finish.strftime('%m-%d'),
'andor': 'and if start.year == finish.year else 'or'
}]
def birthday_on(self, date):
return self.birthday_between(date, date)
Now, I can do things like:
Person.objects.birthday_on(datetime.date.today())
Matching leap-day birthdays only on the day before, or only the day after is also possible: you just need to change the SQL test to a `>=' or '<=', and not adjust the start/finish in the python function.
I'm not overly confident in this, but it seems to work in my testing. The key here is the OVERLAPS operator, and some date arithmetic.
I assume you have a table:
create temporary table birthdays (name varchar, bday date);
Then I put some stuff into it:
insert into birthdays (name, bday) values
('Aug 24', '1981-08-24'), ('Aug 04', '1982-08-04'), ('Oct 10', '1980-10-10');
This query will give me the people with birthdays in the next week:
select * from
(select *, bday + date_trunc('year', age(bday)) + interval '1 year' as anniversary from birthdays) bd
where
(current_date, current_date + interval '1 week') overlaps (anniversary, anniversary)
The date_trunc truncates the date at the year, so it should get you up to the current year. I wound up having to add one year. This suggests to me I have an off-by-one in there for some reason. Perhaps I just need to find a way to get dates to round up. In any case, there are other ways to do this calculation. age gives you the interval from the date or timestamp to today. I'm trying to add the years between the birthday and today to get a date in the current year.
The real key is using overlaps to find records whose dates overlap. I use the anniversary date twice to get a point-in-time.
Finally, to show the upcoming birthdays of the next 14 days I used this:
SELECT
-- 14 days before birthday of 2000
to_char( to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd') - interval '14 days' , 'YYYY-MM-dd') as _14b_b2000,
-- birthday of 2000
to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd') as date_b2000,
-- current date of 2000
to_date(to_char(current_date, '2000-MM-dd'), 'YYYY-MM-dd') as date_c2000,
-- 14 days after current date of 2000
to_char( to_date(to_char(current_date, '2000-MM-dd'), 'YYYY-MM-dd') + interval '14 days' , 'YYYY-MM-dd') as _14a_c2000,
-- 1 year after birthday of 2000
to_char( to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd') + interval '1 year' , 'YYYY-MM-dd') as _1ya_b2000
FROM c
WHERE
-- the condition
-- current date of 2000 between 14 days before birthday of 2000 and birthday of 2000
to_date(to_char(current_date, '2000-MM-dd'), 'YYYY-MM-dd') between
to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd') - interval '14 days' and
to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd')
or
-- 1 year after birthday of 2000 between current date of 2000 and 14 days after current date of 2000
to_date(to_char(c.birthdate, '2000-MM-dd'), 'YYYY-MM-dd') + interval '1 year' between
to_date(to_char(current_date, '2000-MM-dd'), 'YYYY-MM-dd') and
to_date(to_char(current_date, '2000-MM-dd'), 'YYYY-MM-dd') + interval '14 days'
;
So:
To solve the leap-year issue, I set both birthdate and current date to 2000,
and handle intervals only from this initial correct dates.
To take care of the near end/beginning dates,
I compared first the 2000 current date to the 2000 birthday interval,
and in case current date is at the end of the year, and the birthday is at the beginning,
I compared the 2001 birthday to the 2000 current date interval.
Here's a query that gets the right result, most of the time.
SELECT
(EXTRACT(MONTH FROM DATE '1980-08-05'),
EXTRACT(DAY FROM DATE '1980-08-05'))
IN (
SELECT EXTRACT(MONTH FROM CURRENT_DATE + s.a) AS m,
EXTRACT(DAY FROM CURRENT_DATE + s.a) AS d
FROM GENERATE_SERIES(0, 6) AS s(a)
);
(it doesn't take care of leap years correctly; but you could use extract again to work the subselect in terms of a leap year instead of the current year.
EDIT: Got it working for all cases, and as a useful query rather than a scalar select. I'm using some extra subselects so that I don't have to type the same date or expression twice for month and day, and of course the actual data would be in a table instead of the values expression. You might adapt this differently. It might still stand to improve by making a more intelligent series for weeks containing leap days, since sometimes that interval will only contain 6 days (for non-leap years).
I'll try to explain this from the inside-out; First thing I do is normalize the target date (CURRENT_DATE usually, but explicit in this code) into a year that I know is a leap year, so that February 29th appears among dates. The next step is to generate a relation with all of the month-day pairs that are under consideration; Since there's no easy way to do an interval check in terms of month-day, it's all happening using generate_series,
From there it's a simple matter of extracting the month and day from the target relation (the people alias) and filtering just the rows that are in the subselect.
SELECT *
FROM
(select column1 as birthdate, column2 as name
from (values
(date '1982-08-05', 'Alice'),
(date '1976-02-29', 'Bob'),
(date '1980-06-10', 'Carol'),
(date '1992-06-13', 'David')
) as birthdays) as people
WHERE
((EXTRACT(MONTH FROM people.birthdate),
EXTRACT(DAY FROM people.birthdate)) IN (
SELECT EXTRACT(MONTH FROM thedate.theday + s.a) AS m,
EXTRACT(DAY FROM thedate.theday + s.a) AS d
FROM
(SELECT date (v.column1 -
(extract (YEAR FROM v.column1)-2000) * INTERVAL '1 year'
) as theday
FROM (VALUES (date '2011-06-09')) as v) as thedate,
GENERATE_SERIES(0, 6) AS s(a)
)
)
Operating on days, as I've done here, should work splendidly all the way up until a two month interval (if you wanted to look out that far), since december 31 + two months and change should include the leap day. On the other hand, it's almost certainly more useful to just work on whole months for such a query, in which case you don't really need anything more than extract(month from ....
First find out how old the person currently is using age(), then grab the year from that extract(year from age()). This is how old they are currently in years, so for their age at their next birthday add 1 to the year. Then their next birthday is found by adding an interval of this many years * interval '1 year' to their birthday. Done.
I've used a subselect here to add the next_birth_day column in to the complete table to make the select clause simpler. You can then play with the where conditions to suit your needs.
select *
from (
select *,
(extract(year from age(birth_date)) + 1) * interval '1 year' + birth_date "next_birth_day"
from public.users
) as users_with_upcoming_birth_days
where next_birth_day between now() and now() + '7 days'
This is based on Daniel Lyons's anniversary idea, by calculating the interval between the next birthday and today, with just +/- date arithmetic:
SELECT
today,
birthday,
CASE
WHEN this_year_anniversary >= today
THEN this_year_anniversary
ELSE this_year_anniversary + '1 year'::interval
END - today < '1 week'::interval AS is_upcoming
FROM
(
SELECT
today,
birthday,
birthday + years AS this_year_anniversary
FROM
(
SELECT
today,
birthday,
((
extract(year FROM today) - extract(year from birthday)
) || ' years')::interval AS years
FROM
(VALUES ('2011-02-28'::date)) AS t1 (today),
(VALUES
('1975-02-28'::date),
('1975-03-06'::date),
('1976-02-28'::date),
('1976-02-29'::date),
('1976-03-06'::date)
) AS t2 (birthday)
) AS t
) AS t;
In case you want it to work with leap years:
create or replace function birthdate(date)
returns date
as $$
select (date_trunc('year', now()::date)
+ age($1, 'epoch'::date)
- (extract(year from age($1, 'epoch'::date)) || ' years')::interval
)::date;
$$ language sql stable strict;
Then:
where birthdate(birthdate) between current_date
and current_date + interval '1 week'
See also:
Getting all entries who's Birthday is today in PostgreSQL
Exemple: birthdate between: jan 20 and feb 10
SELECT * FROM users WHERE TO_CHAR(birthdate, '1800-MM-DD') BETWEEN '1800-01-20' AND '1800-02-10'
Why 1800?
No matter may be any year;
In my registration form, I can inform the date of birth (with years) or just the birthday (without year), in which case I saved as 1800 to make it easier to work with the date
Here's my take, which works with leap years too:
CREATE OR REPLACE FUNCTION days_until_birthday(
p_date date
) RETURNS integer AS $$
DECLARE
v_now date;
v_days integer;
v_date_upcoming date;
v_years integer;
BEGIN
v_now = now()::date;
IF (p_date IS NULL OR p_date > v_now) THEN
RETURN NULL;
END IF;
v_years = date_part('year', v_now) - date_part('year', p_date);
v_date_upcoming = p_date + v_years * interval '1 year';
IF (v_date_upcoming < v_now) THEN
v_date_upcoming = v_date_upcoming + interval '1 year';
END IF;
v_days = v_date_upcoming - v_now;
RETURN v_days;
END
$$ LANGUAGE plpgsql IMMUTABLE;
I know this post is old, but I had the same issue and came up with this simple and elegant solution:
It is pretty easy with age() and accounts for lap years... for the people who had their birthdays in the last 20 days:
SELECT * FROM c
WHERE date_trunc('year', age(birthdate)) != date_trunc('year', age(birthdate + interval '20 days'))
I have simply created this year date from original birth date.
( DATE_PART('month', birth_date) || '/' || DATE_PART('day', birth_date) || '/' || DATE_PART('year', now()))::date between :start_date and :end_date
I hope this help.
How do I add a dynamic (column based) number of days to NOW?
SELECT NOW() + INTERVAL a.number_of_days "DAYS" AS "The Future Date"
FROM a;
Where a.number_of_days is an integer?
I usually multiply the number by interval '1 day' or similar, e.g.:
select now() + interval '1 day' * a.number_of_days from a;
I know this is a year old, but if you need to use a column to specify the actual interval (e.g. 'days', 'months', then it is worth knowing that you can also CAST your string to an Interval, giving:
SELECT now()+ CAST(the_duration||' '||the_interval AS Interval)
So the the original question would become:
SELECT now() + CAST(a.number_of_days||" DAYS" AS Interval) as "The Future Date" FROM a;
I prefer this way. I think its pretty easy and clean.
In Postgres you need interval to use + operator with timestamp
select (3||' seconds')::interval;
select now()+ (10||' seconds')::interval,now();
where you can use seconds, minutes, days, months...
and you can replace the numbers to your column.
select now()+ (column_name||' seconds')::interval,now()
from your_table;
Use make_interval()
SELECT NOW() + make_interval(days => a.number_of_days) AS "The Future Date"
FROM a;
But in general it might be a better idea to use a column defined as interval, then you can use any unit you want when you store a value in there.
To creating intervals those based on column values, I recommend to add two columns in your table. For example, column "period_value"::INT4 and column "period_name"::VARCHAR.
Column "period_name" can store the following values:
microsecond
milliseconds
second
minute
hour
day
week
month
quarter
year
decade
century
millennium
+--------------+-------------+
| period_value | period_name |
+--------------+-------------+
| 2 | minute |
+--------------+-------------+
Now you can write:
SELECT NOW() - (period_value::TEXT || ' ' || period_name::TEXT)::INTERVAL FROM table;
If we have field with interval string value such as '41 years 11 mons 4 days' and want to convert it to date of birth use this query :
UPDATE "february14" set dob = date '2014/02/01' - (patient_age::INTERVAL)
dob is date field to convert '41 years 11 mons 4 days' to '1972/10/14' for example
patient_age is varchar field that have string like '41 years 11 mons 4 days'
And this is query to convert age back to date of birth
SELECT now() - INTERVAL '41 years 10 mons 10 days';
Updating based on a column ID was a useful way to create some randomised test data for me.
update study_histories set last_seen_at = now() - interval '3 minutes' * id;