Postgres query certain overlapping times on weekdays - postgresql

Question

Imagine you have a set of records for a certain period of time, for example produced products in a month.
Now you want to know how many of those products have been produced at 22 to 3 on Wednesdays and Fridays.
To get all products let's assume the query looks like:
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
where $startOfMonth and $endOfMonth are placeholder values for some integer timestamps.
To get products of a certain time we can make use of "BETWEEN TIME" and add it to the query:
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
AND CAST(timestamp AS time) BETWEEN TIME '3:00' AND TIME '22:00'
Next thing we do is adding the exclusive days we want to query:
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
AND CAST(timestamp AS time) BETWEEN TIME '3:00' AND TIME '22:00'
AND EXTRACT(dow FROM timestamp) IN (3,5)
Everything works fine.
But now I want to query a time overlapping a day:
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
AND CAST(timestamp AS time) BETWEEN TIME '22:00' AND TIME '12:00'
AND EXTRACT(dow FROM timestamp) IN (3,5)
and I don't receive any results.
How to run this query if the starting time is on another day than the ending time?
Thank you ;-)

Answer 1

BETWEEN TIME '3:00' AND TIME '22:00' seems to be the opposite of what you're asking in the question ("produced at 22 to 3").
I think you'll just have to split the time range and use an OR condition, since it crosses midnight. Assuming that "22 to 3" on a Wednesday, you actually mean "22 to midnight" on a Wednesday and "midnight to 3am" on a Thursday (same for Friday/Saturday)
You won't even need BETWEEN, since the lower/upper bounds will be midnight, when the day changes. Something like this should work:
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
AND ((CAST(timestamp AS time) >= TIME '22:00'
AND EXTRACT(dow FROM timestamp) IN (3,5))
OR (CAST(timestamp AS time) < TIME '03:00'
AND EXTRACT(dow FROM timestamp) IN (4,6)))
You may need to adapt this a little if you want to include the timestamps that are on the first Thursday or Saturday of the month (before 3am) into the count for the previous month (if it makes sense for your report): a quick way to do this is to adapt the integer timestamp you provide $endOfMonth to be at 3am on the first day of the following month.
(As a side note, I'd avoid using timestamp as a column name, since it's also a type and can cause confusion.)

Answer 2

Perhaps an easier way is to restate the times in question. That is instead of working with TIMEs a 22:00 and 03:00 consider start time as date+22hours and end time as date+27 hours.(duration of 5 hours from 22:00 - 03:00) Then process with the full timestamp.
SELECT count(id)
FROM products
WHERE timestamp BETWEEN to_timestamp($startOfMonth) AND to_timestamp($endOfMonth)
AND EXTRACT(dow FROM timestamp) IN (3,5)
and timestamp between date_trunc('day', timestamp) + interval '22 hours'
and date_trunc('day', timestamp) + interval '27 hours';
Note: I echo #Bruno on not using timestamp as a column (or any DB object) name. While it is not a Postgres reserved word, Postgres restricts is use and it is a SQL Standard reserved word.