I'm not sure how to check for date ranges using a postgres function. What I want to do is check if a date falls within a certain range (with leeway of a week before the starting date)
So basically, I want to check if a date is between 7 days before to current date, and if so I'll return the id of that row.
create or replace function eight(_day date) returns text as $$
declare
r record;
check alias for $1;
startDate date;
begin
for r in
select * from terms
order by starting;
loop
startDate := r.starting;
if check between (..need help to create 7 days before startDate) and startDate return r.id;
end;
$$ language plpgsql;
I also have to check if the previous record's ending date collides with the startDate - 7days. How would I check the previous record?
Sounds like you want to use an interval:
startDate - interval '...'
I won't say any more than this since you're doing homework.
Dates work with integer math.
startdate - 8 is equivalent to (startdate::timestamp - '8 days'::interval)::date
Related
I am looking for a function in PostgreSQL which help me to generate recurring date after every 90 days from created date
for example: here is a demo table of mine.
id date name
1 "2020-09-08" "abc"
2 "2020-09-08" "xyz"
3 "2020-09-08" "def"
I need furure date like 2020-12-08, 2021-03-08, 2021-06-08, and so on
First it's important to note that, if you happen to have a date represented as text, then you can convert it to a date via:
SELECT TO_DATE('2017-01-03','YYYY-MM-DD');
So, if you happen to have a text as an input, then you will need to convert it to date. Next, you need to know that if you have a date, you can add days to it, like
SELECT CURRENT_DATE + INTERVAL '90 day';
Now, you need to understand that you can use dynamic variables, like:
select now() + interval '1 day' * 180;
Finally, you will need a temporary table to generate several values described as above. Read more here: How to return temp table result in postgresql function
Summary:
create a function
that generates a temporary table
where you insert as many records as you like
having the date shifted
and converting text to date if needed
You can create a function that returns a SETOF dates/timestamps. The below function takes 3 parameters: a timestamp, an interval, the num_of_periods desired. It returns num_of_periods + 1 timestamps, as it returns the original timestamp and the num_of_periods each the specified interval apart.
create or replace
function generate_periodic_time_intervals
( start_date timestamp
, period_length interval
, num_of_periods integer
, out gen_timestamp timestamp
)
returns setof timestamp
language sql
immutable strict
as $$
select (start_date + n * period_length)::timestamp
from generate_series(0,num_of_periods) gs(n)
$$;
For your particular case to timestamp/date as necessary. The same function would work for your case with the interval specified as '3 months' or of '90 days'. Just a note the interval specified can be any valid INTERVAL data type. See here. It also demonstrates the difference between 3 months and 90 days.
I tried to ruh this query in postgres :
Select to_char((select add_months (to_date ('10/10/2019', 'dd/mm/yyyy'), '11/11/2019') ) , 'dd/mm/yyyy') as temp_date
I got an error :
Function add_months (date, unknown) does not exist
Hint: no function matches the given name and argument types. You might need to add explicit type casts.
Please help
As documented in the manual there is no add_months function in Postgres
But you can simply add an interval:
select to_date('10/10/2019', 'dd/mm/yyyy') + interval '10 months'
If you need to format that date value to something:
select to_char(to_date('10/10/2019', 'dd/mm/yyyy') + interval '10 months', 'yyyy-mm-dd')
No one, even running on Oracle, has run the original query- at least not successfully. It appears that query is expecting to add two months together (in this case Oct and Nov). That is not what the function does. It adds an integer number of months to the specified date and returns the resulting date. As indicated in Postgres just adding the desired interval. However, if you have many occurrences ( like converting) of this the following implements a Postgres version.
create or replace function add_months(
date_in date
, n_months_in integer)
returns date
language sql immutable strict
as
$$
-- given a date and an integer for number of months return the calendar date for the specified number of months away.
select (date_in + n_months_in * interval '1 month')::date
$$ ;
-- test
-- +/- 6 months from today.
select current_date "today"
, add_months(current_date,6) "6 months from now"
, add_months(current_date,-6) "6 months ago"
;
I have a simple question regarding T-SQL. I have a stored procedure which calls a Function which returns a date. I want to use an IF condition to compare todays date with the Functions returned date. IF true to return data.
Any ideas on the best way to handle this. I am learning t-sql at the moment and I am more familar with logical conditions from using C#.
ALTER FUNCTION [dbo].[monday_new_period](#p_date as datetime) -- Parameter to find current date
RETURNS datetime
BEGIN
-- 1 find the year and period given the current date
-- create parameters to store period and year of given date
declare #p_date_period int, #p_date_period_year int
-- assign the values to the period and year parameters
select
#p_date_period=period,
#p_date_period_year = [year]
from client_week_uk where #p_date between start_dt and end_dt
-- 2 determine the first monday given the period and year, by adding days to the first day of the period
-- this only works on the assumption a period lasts a least one week
-- create parameter to store the first day of the period
declare #p_start_date_for_period_x datetime
select #p_start_date_for_period_x = min(start_dt)
from client_week_uk where period = #p_date_period and [year] = #p_date_period_year
-- create parameter to store result
declare #p_result datetime
-- add x days to the first day to get a monday
select #p_result = dateadd(d,
case datename(dw, #p_start_date_for_period_x)
when 'Monday' then 0
when 'Tuesday' then 6
when 'Wednesday' then 5
when 'Thursday' then 4
when 'Friday' then 3
when 'Saturday' then 2
when 'Sunday' then 1 end,
#p_start_date_for_period_x)
Return #p_result
END
ALTER PROCEDURE [dbo].[usp_data_to_retrieve]
-- Add the parameters for the stored procedure here
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
IF monday_new_period(dbo.trimdate(getutcdate()) = getutcdate()
BEGIN
-- SQL GOES HERE --
END
Thanks!!
I assume you are working on Sql2008. See documentation of IF and CASE keywords for more details.
CREATE FUNCTION dbo.GetSomeDate()
RETURNS datetime
AS
BEGIN
RETURN '2012-03-05 13:12:14'
END
GO
IF CAST(GETDATE() AS DATE) = CAST(dbo.GetSomeDate() AS DATE)
BEGIN
PRINT 'The same date'
END
ELSE
BEGIN
PRINT 'Different dates'
END
-- in the select query
SELECT CASE WHEN CAST(GETDATE() AS DATE) = CAST(dbo.GetSomeDate() AS DATE) THEN 1 ELSE 0 END AS IsTheSame
This is the basic syntax for a T-SQL IF and a date compare.
If you are comparing just the date portion for equality you will need to use:
select dateadd(dd,0, datediff(dd,0, getDate()))
This snippet will effectively set the time portion to 00:00:00 so you can compare just dates. So in use it will look something like this.
IF dateadd(dd,0, datediff(dd,0, fn_yourFunction())) = dateadd(dd,0, datediff(dd,0, GETDATE()))
BEGIN
RETURN SELECT * FROM SOMEDATA
END
Hope that helps!
I have a relation that maintains monthly historical data. This data is added to the table on the last day of each month. A service I am writing can then be called specifying a month and a number of months prior for which to retrieve the historical data. I am doing this by creating startDate and endDate variables, and then returning data between the two. The problem I am having is that startDate is a variable number of months before endDate, and I cannot figure out how to use a variable period in an interval.
Here is what I have:
DECLARE
endDate TIMESTAMP := (DATE_TRUNC('MONTH',$2) + INTERVAL '1 MONTH') - INTERVAL '1 DAY';
startDate TIMESTAMP := endDate - INTERVAL $3 'MONTH';
I know that the line for startDate is not correct. How is this properly done?
Use this line:
startDate TIMESTAMP := endDate - ($3 || ' MONTH')::INTERVAL;
and note the space before MONTH.
Basically: You construct a string with like 4 MONTH and cast it with ::type into a proper interval.
Edit: I' have found another solution: You can calculate with interval like this:
startDate TIMESTAMP := endDate - $3 * INTERVAL '1 MONTH';
This looks a little bit nicer to me.
This code has nothing directly to do with your situation, but it does illustrate how to use variables in INTERVAL arithmetic. My table's name is "calendar".
CREATE OR REPLACE FUNCTION test_param(num_months integer)
RETURNS SETOF calendar AS
$BODY$
select * from calendar
where cal_date <= '2008-12-31 00:00:00'
and cal_date > date '2008-12-31' - ($1 || ' month')::interval;
$BODY$
LANGUAGE sql VOLATILE
COST 100
ROWS 1000;
The most readable way I have found to pass a variable time period to Postgres is similar to A.H.'s answer: by multiplying by an integer. But this can be done without a cast.
Python example (with sqlalchemy and pandas):
import pandas as pd
import sqlalchemy as sa
connection = sa.create_engine(connection_string)
df = pd.read_sql(
sa.text('''
select * from events
where
event_date between now() - (interval '1 day' * :ndays) and now()
limit 100;
'''),
connection,
params={'ndays': 100}
)
The number of days (ndays) is passed as an integer from within Python - so unintended consequences are less likely.
My approach is like this.. It gives me option to set specific date or a relative range.
create or replace function search_data(_time_from timestamptz default null, _last_interval text default null)
returns setof journal
language plpgsql as
$$
begin
return query
select *
from journal
where created >= case
when _time_from is not null
then _time_from
else now() - _last_interval::interval end;
end;
$$;
While the above accepted answer is fine, it's a little bit antiquated - requiring a bit more mental energy to read than needed if you're running on Postgres 9.4+.
Old Way (Postgres Versions < 9.4)
startDate TIMESTAMP := endDate - $3 * INTERVAL '1 MONTH';
New Way (Postgres 9.4+)
startDate TIMESTAMP := endDate - MAKE_INTERVAL(MONTHS => $3);
If you are on Postgres 9.4+, the new MAKE_INTERVAL() function seems much more readable - probably why they created it.
If you want something you can run in your editor, here are a couple of
examples (I substituted the original variable binding $3 with the number 2 for an example of 2-months prior to the current date).
SELECT CURRENT_DATE - 2 * INTERVAL '1 MONTH';
SELECT CURRENT_DATE - MAKE_INTERVAL(MONTHS => 2);
CREATE PROCEDURE sp_ME
#ID int,
#ThisDate datetime = null
AS
SET NOCOUNT ON
IF #ThisDate IS NULL
BEGIN
SET #ThisDate = CURRENT_TIMESTAMP
END
DECLARE #intErrorCode int,
#QBegin datetime,
#QEnd datetime
SELECT #intErrorCode = ##ERROR
IF #ThisDate BETWEEN '01/01/' + CONVERT(VARCHAR(4), YEAR(#ThisDate))
AND '03/31/' + CONVERT(VARCHAR(4), YEAR(#ThisDate))
BEGIN
Select #QBegin = DATEADD(s,0,CAST ('10/01/' AS varchar(6) ) +
CONVERT(VARCHAR(4),DATEPART (year,#ThisDate)-1))
Select #QEnd = DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,#QBegin)+3,0))
SELECT * FROM QUERY
WHERE MEID = #ID
AND mydate >= #QBegin
AND mydate <= #QEnd)
END
SELECT #intErrorCode = ##ERROR
IF (#intErrorCode <> 0) GOTO ErrHandler
ErrHandler:
RETURN #intErrorCode
GO
It returns a dataset when you leave it blank and it assumes and fills in the date, however when you plug in a date it just states "The command completed successfully."
Any help would be more than appreciated.
At a guess, you need to query the previous quarter's results, which would just be this query:
SELECT * FROM QUERY
WHERE MEID = #ID
AND mydate >= DATEADD(quarter,DATEDIFF(quarter,'20010101',#ThisDate),'20001001'),
AND mydate < DATEADD(quarter,DATEDIFF(quarter,'20010101',#ThisDate),'20010101'))
And get rid of that big if condition, etc.
You could also get rid of the first if, if you put COALESCE(#ThisDate,CURRENT_TIMESTAMP) in the above, where I currently have #ThisDate.
I use the DATEADD(quarter,DATEDIFF(quarter,'20010101',#ThisDate),'20001001') pattern for a lot of datetime manipulation. It let's you achieve a lot in a few operations. In this case, it's the difference between the two dates ('20010101','20001001') which is giving us the previous quarter.
You'll frequently encounter the DATEADD/DATEDIFF pattern in questions involving removing the time portion from a datetime value. The canonical version of this is DATEADD(day,DATEDIFF(day,0,#Date),0). But the pattern can be generally extended to work with any of the datetime components. If you choose month rather than day, you'll get midnight at the start of the first of the month (of the day you've supplied)
Where it gets tricky is when you use dates (instead of 0), and especially if you don't use the same date for both calculations. This allows you to apply an additional offset that seems almost "free" - you're already using this construct to remove the time component, the fact that you can compute e.g. the last date in a quarter/month/etc is a bonus.