Question

Assume all value columns have the same datatype. I would like the highest of all values with the id in the results of a SELECT query.

Table Structure:

table_a: id, value1, value2, value3, value4, value5

Example data:

id, value1, value2, value3, value4, value5
2, 125, 256, 133, 400, 67
3, 14, 14, 14, 3, 6
4, 325, 441, 441, 975, 3

Example desired results:

id, highest_value
2, 400
3, 14
4, 975

I started down the path of a CASE statement but that got messy fast. I tired a sub-select but failed in getting that to work. Is there a clean way to compare several column values to each other?

Answer 1

In this case greatest function will do the work.

with t1(id1, val1, val2, val3, val4, val5) as
(
  select 2, 125, 256, 133, 400, 67 from dual union all
  select 3, 14,  14,  14,  3,   6  from dual union all
  select 4, 325, 441, 441, 975, 3  from dual
)

select id1 
     , greatest(val1, val2, val3, val4, val5) Res
  from t1

Result:

Id1 Res 
---------------
2   400 
3   14 
4   975