2025
Otus - Small Tricks of Group By 0:00 of 1:31:23
    https://www.youtube.com/watch?v=yj27kupwrMQ

having
    (where works before aggregations calculation)

https://www.postgresql.org/docs/current/functions-aggregate.html

https://www.postgresql.org/docs/current/queries-table-expressions.html#QUERIES-GROUP

=> SELECT * FROM test1;
 x | y
---+---
 a | 3
 c | 2
 b | 5
 a | 1
(4 rows)

=> SELECT x, sum(y) FROM test1 GROUP BY x;
 x | sum
---+-----
 a |   4
 b |   5
 c |   2
(3 rows)

select field1, field2, count(*) as cnt
from tbl
where field-date >= now() - '30 days'::interval and ...
group by field1, field2
having count(*) > 1;