SQL: select original highest absolute value

Question

WITH base AS (
    SELECT 'ID1' as id, 0 as foo
    UNION
    SELECT 'ID1' as id, -1 as foo
    UNION
    SELECT 'ID2' as id, 2 as foo
    UNION 
    SELECT 'ID2' as id, null as foo
    UNION 
    SELECT 'ID2' as id, -1 as foo
    UNION 
    SELECT 'ID2' as id, 1 as foo
)
select
    id
   ,MAX(CASE WHEN char_length(foo) > 0 THEN foo ELSE NULL END)
from base
GROUP BY id
ORDER BY id ASC

This query returns 0 for the ID1 and 2 for the ID2.

What I'd like to have, is a SELECT expression that's going to return -1 for the ID1 and 2 for the ID2.

MAX(ABS()) is almost what I want, but it returns 1 and not -1 . I can't use JOIN and anything else, only a SELECT expression. Any ideas?

Answer 1

Here is one way to solve it:

select
    id
   ,MAX(ABS(foo)) * CASE WHEN ABS(MIN(foo)) > MAX(foo) THEN -1 ELSE 1 END As MaxAbs
from base
GROUP BY id
ORDER BY id ASC

Results:

id      MaxAbs
ID1     -1
ID2     2