Question: I am using w2ui (1.5) and I would be interested in whether it is possible to use a filter that only delivers negative results

That means only records/keys which not fullfilling a certain criteria.

Like a condition "contains not" or "is not" in addition to

<http://w2ui.com/web/docs/1.5/w2grid.textSearch>.

Thanks!
Gordon

Answer: 
You can check whether there are nulls by getting the maximum of `VALIDTO is null` in that group:

```
select 
    field1, field2, 
    case when max(VALIDTO is null) = False then max(VALIDTO) end as VALIDTO
from test_table
group by field1, field2

```
Hmmm . . . I think you want an aggregation function on `validto` to return `NULL` if *any* values are `NULL`. If so, you can use `case`:

```
(case when count(*) = count(validTo) then max(validTo)
 end)

```