Select max from calculated column alongside other columns - sql

Question

I have a table that has columns ID, FIELD1, FIELD2, all of type NUMBER.
I want to find the MAX of a function on FIELD1 and FIELD2, and display that alongside the ID.
I try
SELECT ID, MAX(SQRT(FIELD1 + FIELD2)) AS CALC
FROM TABLE;
But it returns ORA-00937: not a single-group group function.
I tried the solutions in this thread, but they have their own errors.
SELECT * FROM (
SELECT ID, SQRT(FIELD1 + FIELD2) AS CALC,
RANK() OVER (ORDER BY CALC DESC) AS RANKING
FROM TABLE
)
WHERE RANKING = 1;
gives the error
ORA-06553: PLS-306: wrong number or types of arguments in call to
'OGC_CALC'
and so does
SELECT ID, SQRT(FIELD1 + FIELD2) AS CALC
FROM TABLE
WHERE CALC = (
SELECT MAX(CALC)
FROM TABLE
);
Using Oracle Database 11g Express Edition Release 11.2.0.2.0.
How can I get this to work? Thanks.

Answer 1

Can you try the below two queries.
SELECT ID,FIELD1,FIELD2,SQRT(FIELD1 + FIELD2) AS CALC
FROM TABLE WHERE SQRT(FIELD1 + FIELD2)= (SELECT MAX(SQRT(FIELD1 + FIELD2)) FROM TABLE);
Or,
Suggested by Aleksej without using aggregate or group by function.
SELECT *
FROM (
SELECT ID,
SQRT(FIELD1 + FIELD2)
FROM TABLE
ORDER BY 2 DESC
)
WHERE ROWNUM=1;
Initial query,
SELECT *
FROM (
SELECT ID,
MAX(SQRT(FIELD1 + FIELD2)) AS CALC
FROM TABLE
GROUP BY ID
ORDER BY 2 DESC
)
WHERE ROWNUM=1;

Answer 2

If you need a single value, with the maximum sqrt(field1+field2) among all the values of ID, these are two possible ways:
select *
from (
select *
from yourTable
order by sqrt(field1 + field2) desc
)
where rownum = 1
select id, field1, field2
from (
select t.*,
row_number() over ( order by sqrt(field1 + field2) desc) as rn
from yourTable t
)
where rn = 1
Notice that if you have more than one ID with the same, maximum value, this will pick one of them randomly.