On Sun, Jun 30, 2024 at 3:51 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Igal Sapir <igal@xxxxxxxxx> writes:
> But this throws an error (SQL Error [42601]: ERROR: syntax error at or near
> "'1 '"):
> SELECT generate_series(
> date_trunc('month', current_date),
> date_trunc('month', current_date + interval '7 month'),
> interval ('1 ' || 'month')::interval
> )
You're overthinking it.
SELECT generate_series(
date_trunc('month', current_date),
date_trunc('month', current_date + interval '7 month'),
('1 ' || 'month')::interval
);
generate_series
------------------------
2024-06-01 00:00:00-04
2024-07-01 00:00:00-04
2024-08-01 00:00:00-04
2024-09-01 00:00:00-04
2024-10-01 00:00:00-04
2024-11-01 00:00:00-04
2024-12-01 00:00:00-05
2025-01-01 00:00:00-05
(8 rows)
Thank you, Tom. I thought that I tried that too, but apparently I did not because it works the way you wrote it.
It might help to read this:
https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS-GENERIC
and to experiment with what you get from the constituent elements
of what you tried, rather than trying to guess what they are from
generate_series's behavior. For example,
select (interval '1 ');
interval
----------
00:00:01
(1 row)
select (interval '1 ' || 'month');
?column?
---------------
00:00:01month
(1 row)
I actually did test the _expression_ that I posted, but it might be casting it twice. While your examples that you wrote show 1 month correctly:
SELECT (interval '1 ' || 'month');
?column? |
-------------+
00:00:01month|
-------------+
00:00:01month|
SELECT ('1 ' || 'month')::interval;
interval|
--------+
1 mon|
--------+
1 mon|
When the _expression_ includes the "::interval" suffix as in the example that I posted it returns 1 second, possibly because it is casting to interval twice (at least on PostgreSQL 16.2 (Debian 16.2-1.pgdg120+2)):
SELECT (interval '1 ' || 'month')::interval;
interval|
--------+
00:00:01|
--------+
00:00:01|
Anyway, you solved my issue, so thank you very much as always,
Igal
regards, tom lane
