generate_series() equivalent in snowflake - sql

Question

I'm trying to find the snowflake equivalent of generate_series() (the PostgreSQL syntax).
SELECT generate_series(timestamp '2017-11-01', CURRENT_DATE, '1 day')

Answer 1

Just wanted to expand on Marcin Zukowski's comment to say that these gaps started to show up almost immediately after using a date range generated this way in a JOIN.
We ultimately ended up doing this instead!
select
dateadd(
day,
'-' || row_number() over (order by null),
dateadd(day, '+1', current_date())
) as date
from table (generator(rowcount => 90))

Answer 2

I had a similar problem and found an approach, which avoids the issue of a generator requiring a constant value by using a session variable in addition to the already great answers here. This is closest to the requirement of the OP to my mind.
-- set parameter to be used as generator "constant" including the start day
set num_days = (Select datediff(day, TO_DATE('2017-11-01','YYYY-MM-DD'), current_date()+1));
-- use parameter in bcrowell's answer now
select
dateadd(
day,
'-' || row_number() over (order by null),
dateadd(day, '+1', current_date())
) as date
from table (generator(rowcount => ($num_days)));
-- clean up previously set variable
unset num_days;

Answer 3

WITH RECURSIVE rec_cte AS (
-- start date
SELECT '2017-11-01'::DATE as dt
UNION ALL
SELECT DATEADD('day',1,dt) as dt
FROM rec_cte
-- end date (inclusive)
WHERE dt < current_date()
)
SELECT * FROM rec_cte

Answer 4

Adding this answer for completitude, in case you have an initial and last date:
select -1 + row_number() over(order by 0) i, start_date + i generated_date
from (select '2020-01-01'::date start_date, '2020-01-15'::date end_date)
join table(generator(rowcount => 10000 )) x
qualify i < 1 + end_date - start_date

Answer 5

I found the generator function in Snowflake quite limiting for all but the simplest use cases. For example, it was not clear how to take a single row specification, explode it into a table of dates and join it back to the original spec table.
Here is an alternative that uses recursive CTEs.
-- A 2 row table that contains "specs" for a date range
create local temp table date_spec as
select 1 as id, '2022-04-01'::date as start_date, current_date() as end_date
union all
select 2, '2022-03-01', '2032-03-30'
;
with explode_date(id, date, next_date, end_date) as (
select
id
, start_date as date -- start_date is the first date
, date + 1 as next_date -- next_date is the date of for the subsequent row in the recursive cte
, end_date
from date_spec
union all
select
ds.id
, ed.next_date -- the current_date is the value of next_date from above
, ed.next_date + 1
, ds.end_date
from date_spec ds
join explode_date ed
on ed.id = ds.id
where ed.date <= ed.end_date -- keep running until you hit the end_date
)
select * from explode_date
order by id, date desc
;

Answer 6

This is how I was able to generate a series of dates in Snowflake. I set row count to 1095 to get 3 years worth of dates, you can of course change that to whatever suits your use case
select
dateadd(day, '-' || seq4(), current_date()) as dte
from
table
(generator(rowcount => 1095))
Originally found here
EDIT: This solution is not correct. seq4 does not guarantee a sequence without gaps. Please follow other answers, not this one. Thanks #Marcin Zukowski for pointing that out.