On Sun, Jun 30, 2024 at 3:51 PM Tom Lane <t...@sss.pgh.pa.us> wrote:
> Igal Sapir <i...@lucee.org> 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| SELECT ('1 ' || 'month')::interval; interval| --------+ 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| Anyway, you solved my issue, so thank you very much as always, Igal > > regards, tom lane >