Get the whole part of a decimal number without rounding

Can you please add some example data for f1?
The CASE expression, to me, is not part of your question.
In Vertica, :: is the CAST operator. And casting leads to rounding. To get the integral part of a numeric with decimal fractions, I would use the FLOOR() function.
Maybe the micro demo below sheds some light on what you're searching for.
Whatever you want to do with your CASE expression afterwards is up to you:
WITH
numerics(num) AS (
SELECT 0.125
UNION ALL SELECT 0.25
UNION ALL SELECT 0.375
UNION ALL SELECT 0.5
UNION ALL SELECT 0.625
UNION ALL SELECT 0.75
UNION ALL SELECT 0.875
UNION ALL SELECT 1
)
SELECT
num
, num::INT
, FLOOR(num)::INT
, CEIL(num)::INT
FROM numerics;

num |num|FLOOR|CEIL
0.125| 0| 0| 1
0.250| 0| 0| 1
0.375| 0| 0| 1
0.500| 1| 0| 1
0.625| 1| 0| 1
0.750| 1| 0| 1
0.875| 1| 0| 1
1.000| 1| 1| 1

Hi!

dbadmin=> select f1, f1 // 3600 from ismael;
  f1   | ?column? 
-------+----------
  3000 |        0
  3200 |        0
  3400 |        0
  3600 |        1
  3800 |        1
  3900 |        1
  3999 |        1
 13320 |        3
(11 rows)

Good Luck.

Thanks so much Solved