How to hide rows where aggregate functions are used

let’s imagine here is my report:

select 1 from dual
union all
select 2 from dual
union all
select 3 from dual
union all
select 4 from dual

Output:

1
2
3
4

If e.g. i want to hide part of the report in an easy way I simply add 1 = 2 to where clause:

select 1 from dual
union all
select 2 from dual
union all
select 3 from dual where 1 = 2
union all
select 4 from dual

Output:

1
2
4

Cool! However, when select uses aggregate functions, this trick does not help. The row is generated anyway:

select 1 from dual
union all
select 2 from dual
union all
select max(3) from dual where 1 = 2
union all
select 4 from dual

Output:

1
2
(null)
4

Someone maybe know a simple, easy way to hide such rows?

Answer

An aggregation query with no group by always returns exactly one row — even if no rows are being aggregated.

You want to filter after the aggregation, so use having:

select max(3) from dual having 1 = 2