Need to split datetime ranges by each day - sql

I have a table that needs to be split on the basis of datetime
Input Table
ID| Start | End
--------------------------------------------
A | 2019-03-04 23:18:04| 2019-03-04 23:21:25
--------------------------------------------
A | 2019-03-04 23:45:05| 2019-03-05 00:15:14
--------------------------------------------
Required Output
ID| Start | End
--------------------------------------------
A | 2019-03-04 23:18:04| 2019-03-04 23:21:25
--------------------------------------------
A | 2019-03-04 23:45:05| 2019-03-04 23:59:59
--------------------------------------------
A | 2019-03-05 00:00:00| 2019-03-05 00:15:14
--------------------------------------------
Thanks!!

Try this below code. This will only work if the start and end date fall in two consecutive day. Not if the start and end date difference is more than 1 day.
MSSQL:
SELECT ID,[Start],[End]
FROM Input_Table A
WHERE DATEDIFF(DD,[Start],[End]) = 0
UNION ALL
SELECT ID,[Start], CAST(CAST(CAST([Start] AS DATE) AS VARCHAR(MAX)) +' 23:59:59' AS DATETIME)
FROM Input_Table A
WHERE DATEDIFF(DD,[Start],[End]) > 0
UNION ALL
SELECT ID,CAST(CAST([End] AS DATE) AS DATETIME),[End]
FROM Input_Table A
WHERE DATEDIFF(DD,[Start],[End]) > 0
ORDER BY 1,2,3
PostgreSQL:
SELECT ID,
TO_TIMESTAMP(startDate,'YYYY-MM-DD HH24:MI:SS'),
TO_TIMESTAMP(endDate, 'YYYY-MM-DD HH24:MI:SS')
FROM mytemp A
WHERE DATE_PART('day', endDate::date) -
DATE_PART('day',startDate::date) = 0
UNION ALL
SELECT ID,
TO_TIMESTAMP(startDate,'YYYY-MM-DD HH24:MI:SS'),
TO_TIMESTAMP(CONCAT(CAST(CAST (startDate AS DATE) AS VARCHAR) ,
' 23:59:59') , 'YYYY-MM-DD HH24:MI:SS')
FROM mytemp A
WHERE DATE_PART('day', endDate::date) -
DATE_PART('day',startDate::date) > 0
UNION ALL
SELECT ID,
TO_TIMESTAMP(CAST(CAST (endDate AS DATE) AS VARCHAR) ,
'YYYY-MM-DD HH24:MI:SS') ,
TO_TIMESTAMP(endDate,'YYYY-MM-DD HH24:MI:SS')
FROM mytemp A
WHERE DATE_PART('day', endDate::date) -
DATE_PART('day',startDate::date) > 0;
PostgreSQL Demo Here

demo:db<>fiddle
This works even when range crosses more than one day
WITH cte AS (
SELECT
id,
start_time,
end_time,
gs,
lag(gs) over (PARTITION BY id ORDER BY gs) -- 2
FROM
a
LEFT JOIN LATERAL
generate_series(start_time::date + 1, end_time::date, interval '1 day') gs --1
ON TRUE
)
SELECT -- 3
id,
COALESCE(lag, start_time) AS start_time,
gs - interval '1 second'
FROM
cte
WHERE gs IS NOT NULL
UNION
SELECT DISTINCT ON (id) -- 4
id,
CASE WHEN start_time::date = end_time::date THEN start_time ELSE end_time::date END, -- 5
end_time
FROM
cte
CTE: the generate_series function generates one row per day new day. So, there is no value if there is no date change
CTE: the lag() window function allows to move the current date value into the next row (the current end is the next start)
With this data set you can calculate the new start and end values. If there is no gs value: There is no date change. This ignored at this point. For all cases with date changes: If there is no lag value, it is the beginning (so it cannot got a previous value). In this case, the normal start_time is taken, otherwise it is a new day which takes the date break time. The end_time is taken with the last second of the day (interval - '1 second')
The second part: Because of the date breaks there is always one additional record which need to be unioned. The last record is from the beginning of the end_time (so cast to date). The CASE clause combines this step with the case of no date change which has been ignored so far. So if start_time and end_time are at the same date, here the original start_time is taken.

Unfortunately, Redshift doesn't have a convenient way to generate a series of numbers. If you table is big enough, you can use it to generate numbers. "Big enough" means that the number of rows is greater than the longest span. Perhaps another table would work, if not this one.
Once you have that, you can use this logic:
with n as (
select row_number() over () - 1 as n
from t
)
select t.id,
greatest(t.s, date_trunc('day', t.s) + n.n * interval '1 day') as s,
least(t.e, date_trunc('day', t.s) + (n.n + 1) * interval '1 day' - interval '1 second') as e
from t join
n
on t.e >= date_trunc('day', t.s) + n.n * interval '1 day';
Here is a db<>fiddle. It uses an old version of Postgres, but not quite old enough for Redshift.

Simulate loop for interval generation using recursive CTE, i.e. take range from start to midnight in seed row, take another day in subsequent rows etc.
with recursive input as (
select 'A' as id, timestamp '2019-03-04 23:18:04' as s, timestamp '2019-03-04 23:21:25' as e union
select 'A' as id, timestamp '2019-03-04 23:45:05' as s, timestamp '2019-03-05 00:15:14' as e union
select 'B' as id, timestamp '2019-03-06 23:45:05' as s, timestamp '2019-03-08 00:15:14' as e union
select 'C' as id, timestamp '2019-03-10 23:45:05' as s, timestamp '2019-03-15 00:15:14' as e
), generate_id as (
select row_number() over () as unique_id, * from input
), rec (unique_id, id, s, e) as (
select unique_id, id, s, least(e, s::date::timestamp + interval '1 day')
from generate_id seed
union
select remaining.unique_id, remaining.id, previous.e, least(remaining.e, previous.e::date::timestamp + interval '1 day')
from rec as previous
join generate_id remaining on previous.unique_id = remaining.unique_id and previous.e < remaining.e
)
select id, s, e from rec
order by id,s,e
Note:
your id column appears not to be unique, so I added custom unique_id column. If id was unique, CTE generate_id was unnecessary. Uniqueness is unavoidable for recursive query to work.
close-open range is better for representation of such data, rather than close-close range. So end time in my query returns 00:00:00, not 23:59:59. If it's not suitable for you, modify query as an exercise.
UPDATE: query works on Postgres. OP originally tagged question postgres, then changed tag to redshift.

Related

SQL Query to group dates and includes different dates in the aggregation

I have a table with two columns, dates and number of searches in each date. What I want to do is group by the dates, and find the sum of number of searches for each date.
The trick is that for each group, I also want to include the number of searches for the date exactly the following week, and the number of searches for the date exactly the previous week.
So If I have
Date
Searches
2/3/2023
2
2/10/2023
4
2/17/2023
1
2/24/2023
5
I want the output for the 2/10/2023 and 2/17/2023 groups to be
Date
Sum
2/10/2023
7
2/17/2023
10
How can I write a query for this?
You can use a correlated query for this:
select date, (
select sum(searches)
from t as x
where x.date between t.date - interval '7 day' and t.date + interval '7 day'
) as sum_win
from t
Replace interval 'x day' with the appropriate date add function for your RDBMS.
If your RDBMS supports interval in window functions then a much better solution would be:
select date, sum(searches) over (
order by date
range between interval '7 day' preceding and interval '7 day' following
) as sum_win
from t
Assuming weekly rows
CREATE TABLE Table1
([Dates] date, [Searches] int)
;
INSERT INTO Table1
([Dates], [Searches])
VALUES
('2023-02-03 00:00:00', 2),
('2023-02-10 00:00:00', 4),
('2023-02-17 00:00:00', 1),
('2023-02-24 00:00:00', 5)
;
;with cte as (
select dates
, searches
+ lead(searches) over(order by dates)
+ lag(searches) over(order by dates) as sum_searches
from table1)
select * from cte
where sum_searches is not null;
dates
sum_searches
2023-02-10
7
2023-02-17
10
fiddle

Rewrite PostgreSQL query using CTE:

I have the following code to pull records from a daterange in PostgreSQL, it works as intended. The "end date" is determined by the "date" column from the last record, and the "start date" is calculated by subtracting a 7-day interval from the "end date".
SELECT date
FROM files
WHERE daterange((
(SELECT date FROM files ORDER BY date DESC LIMIT 1) - interval '7 day')::date, -- "start date"
(SELECT date FROM files ORDER BY date DESC LIMIT 1)::date, -- "end date"
'(]') #> date::date
ORDER BY date ASC
I'm trying to rewrite this query using CTEs, so I can replace those subqueries with values such as end_date and start_date. Is this possible using this method or should I look for other alternatives like variables? I'm still learning SQL.
WITH end_date AS
(
SELECT date FROM files ORDER BY date DESC LIMIT 1
),
start_date AS
(
SELECT date FROM end_date - INTERVAL '7 day'
)
SELECT date
FROM files
WHERE daterange(
start_date::date,
end_date::date,
'(]') #> date::date
ORDER BY date ASC
Right now I'm getting the following error:
ERROR: syntax error at or near "-"
LINE 7: SELECT date FROM end_date - INTERVAL '7 day'
You do not need two CTEs, it's one just fine, which can be joined to filter data.
WITH RECURSIVE files AS (
SELECT CURRENT_DATE date, 1 some_value
UNION ALL
SELECT (date + interval '1 day')::date, some_value + 1 FROM files
WHERE date < (CURRENT_DATE + interval '1 month')::date
),
dates AS (
SELECT
(MAX(date) - interval '7 day')::date from_date,
MAX(date) to_date
FROM files
)
SELECT f.* FROM files f
JOIN dates d ON daterange(d.from_date, d.to_date, '(]') #> f.date
You even can make it to be a daterange initially in CTE and use it later like this
WITH dates AS (
SELECT
daterange((MAX(date) - interval '7 day')::date, MAX(date), '(]') range
FROM files
)
SELECT f.* FROM files f
JOIN dates d ON d.range #> f.date
Here the first CTE is used just to generate some data.
It will get all file lines for dates in the last week, excluding from_date and including to_date.
date
some_value
2022-09-26
25
2022-09-27
26
2022-09-28
27
2022-09-29
28
2022-09-30
29
2022-10-01
30
2022-10-02
31
I think this is what you want:
WITH end_date AS
(
SELECT date FROM files ORDER BY date DESC LIMIT 1
),
start_date AS
(
SELECT date - INTERVAL '7 day' as date
FROM end_date
)
SELECT F.date, S.date startDate, E.date endDate
FROM files F
JOIN start_date S on F.date >= S.date
JOIN end_date E on F.date <= E.date
ORDER BY date ASC;
I hope I'm not repeating anything, but if I understand your problem correctly I think this will work:
with cte as (
select max (date)::date as max_date from files
)
select date
from files
cross join cte
where date >= max_date - 7
Or perhaps even:
select date
from files
where date >= (select max (date)::date - 7 from files)
Since you have already determined that the CTE has the max date, there is really no need to further bound it with a between, <= or range. You can simply say anything after that date minus 7 days.
The error in your code above is because you want this:
SELECT date - INTERVAL '7 day' as date FROM end_date
And not this:
SELECT date FROM end_date - INTERVAL '7 day'
You are subtracting from the table, which doesn't make sense.

create table with dates - sql

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.

how to get date different in postgres using date_part option

How to get date time difference in PostgreSQL
I am using below syntax
select id, A_column,B_column,
(SELECT count(*) AS count_days_no_weekend
FROM generate_series(B_column ::timestamp , A_column ::timestamp, interval '1 day') the_day
WHERE extract('ISODOW' FROM the_day) < 5) * 24 + DATE_PART('hour', B_column::timestamp-A_column ::timestamp ) as hrs
FROM table req where id='123';
If A_column=2020-05-20 00:00:00 and B_column=2020-05-15 00:00:00 I want to get 72(in hours).
Is there any possibility to skip weekends(Saturday and Sunday) in first one, it means to get the result as 72 hours(exclude weekend hours)
i am getting 0
But i need to get 72 hours
And if If A_column=2020-08-15 12:00:00 and B_column=2020-08-15 00:00:00 I want to get 12(in hours).
One option uses a lateral join and generate_series() to enumerate each and every hour between the two timestamps, while filtering out week-ends:
select t.a_column, t.b_column, h.count_hours_no_weekend
from mytable t
cross join lateral (
select count(*) count_hours_no_weekend
from generate_series(t.b_column::timestamp, t.a_column::timestamp, interval '1 hour') s(col)
where extract('isodow' from s.col) < 5
) h
where id = 123
I would attack this by calculating the weekend hours to let the database deal with daylight savings time. I would then subtract the intervening weekend hours from the difference between the two date values.
with weekend_days as (
select *, date_part('isodow', ddate) as dow
from table1
cross join lateral
generate_series(
date_trunc('day', b_column),
date_trunc('day', a_column),
interval '1 day') as gs(ddate)
where date_part('isodow', ddate) in (6, 7)
), weekend_time as (
select id,
sum(
least(ddate + interval '1 day', a_column) -
greatest(ddate, b_column)
) as we_ival
from weekend_days
group by id
)
select t.id,
a_column - b_column as raw_difference,
coalesce(we_ival, interval '0') as adjustment,
a_column - b_column -
coalesce(we_ival, interval '0') as adj_difference
from weekend_time w
left join table1 t on t.id = w.id;
Working fiddle.

Postgres - Fast way to sum over rows from last day of month

I want to query a table and sum a column for all of the rows from the last day of the month.
Let's use the following table as an example:
CREATE TABLE example(dt date, value int)
(The real table has many more columns and is relatively large, and the real query is more complicated)
I have the following query:
SELECT dt, SUM(value)
FROM example
WHERE dt IN (SELECT DISTINCT
date_trunc('MONTH', generate_series('2012-01-01'::date,
'2016-12-01'::date,
interval '1 day') + INTERVAL '1 MONTH - 1 day')::date)
GROUP BY dt
It runs in about ~2 seconds on my real table.
However, if I generate the full list of end-of-month days in my range and parameterise the query like so:
SELECT dt, SUM(value)
FROM example
WHERE dt IN ('2012-01-31', ...)
GROUP BY dt
It's much quicker, ~750ms.
I would prefer not to generate the dates and pass them through to the query like that, is there a way I can do this entirely in SQL and make it as fast as the latter version?
The sub-select is needlessly complicated. It can be simplified to:
SELECT dt, SUM(value)
FROM example
WHERE dt IN (SELECT d::date
from generate_series('2012-01-01'::date, '2016-12-01'::date, interval '1 month') dates (d)
GROUP BY dt; --<< the group by is necessary
Maybe that speeds up the query.
You can also try to put the date generation into a CTE:
with dates (d) as (
SELECT t::date
from generate_series('2012-01-01'::date, '2016-12-01'::date, interval '1 month') t
)
SELECT dt, SUM(value)
FROM example
WHERE dt IN ( select d from dates)
GROUP BY dt;
Sometimes doing a JOIN is also more efficient:
with dates (d) as (
SELECT t::date
from generate_series('2012-01-01'::date, '2016-12-01'::date, interval '1 month') t
)
SELECT dt, SUM(value)
FROM example
JOIN dates on example.dt = dates.d
GROUP BY dt;
The performance problem in your query comes from the fact that you are generating a daily series. Change it to monthly, remove the distinct and add a group by
select dt, sum(value)
from
example
inner join (
select date_trunc('month', dt) + interval '1 month - 1 day' as dt
from generate_series('2012-01-01'::date, '2016-12-01', '1 month') gs (dt)
) d using (dt)
group by dt