First negative number row in Oracle

Assuming you have a column for sorting, which defines the order of the rows, it could look like this:

with t as (
select 77  a, 1  row_order  from dual union all
select 74  a, 2 row_order from dual union all
select 67  a, 3 row_order from dual union all
select 56  a, 4 row_order from dual union all
select 42  a, 5 row_order from dual union all
select 24  a, 6 row_order from dual union all
select 20  a, 7 row_order from dual union all
select 19  a, 8 row_order from dual union all
select -17 a, 9 row_order from dual union all
select -28 a, 10 row_order from dual union all
select -31 a, 11 row_order from dual union all
select -36 a, 12 row_order from dual
), t1 as (
select a, row_number() over (partition by case when a < 0 then 0 else 1 end order by row_order) rn from t
)
select * from t1 where rn = 1 and a < 0;

It's using a window function in order to determine the first rows (here for positive a's and negative a's) Then it selects the first row encountered that is negative.

If you want the complete row, you can use:

select t.*
from t
where n < 0
order by n asc
fetch first 1 row only;

If you have another column that specifies the ordering of the rows, then:

select t.*
from t
where n < 0
order by <ordering col> asc
fetch first 1 row only;

To select the maximum negative number you can do:

select max(n)
from t
where n < 0

Remember that in relational database tables, rows do not have inherent ordering. Therefore, in the absence of an ordering criteria, there's no such a thing as "first row where the negative value starts".