Should MAX in Group By Retrieve the Whole Row Data - mysql

Question

I have a bunch of sql columns to retrieve. This is my SQL statement:
SELECT b.iposx_model_id,
a.mrModel, MAX(a.mrRevision) as mrRevision, a.mrApprovedBy, ...
FROM mydb1.tbl_model_revision a
INNER JOIN mydb2.model_from_revision_process b
ON b.mrModel = a.mrModel
WHERE a.mrType = 1
GROUP BY a.mrModel
ORDER BY b.iposx_model_id ASC
On a certain mrModel column taht I retrieved, these are the data that I'm querying for:
In my query, it states that I should get the data with the Max mrRevision which corresponds to the third row.
However, upon running the sql statement, I got the max mrRevision which is 2, coming from the third row. But the other column data I get came from the 2nd row, an example is mrApprovedBy which is 1035 instead of 10. Why is that happening?

Answer 1

The use group by for only a part of the column not involved in aggegation function is select clause
is depreacted in SQL because where work produce unpredicatble result
In most DB and in the most recent version of mysql this use of group by is not allowed
for obtain the row corresponding to the max value you could use a join on the values that match the right content
SELECT
b.iposx_model_id
, a.mrModel
, t.mrRevision
, a.mrApprovedBy
, ...
FROM mydb1.tbl_model_revision a
JOIN (
select mrModel, MAX(mrRevision) as mrRevision
from mydb1.tbl_model_revision
GROUP BY a.mrModel
) t on a.mrModel = t.mrModel and a.mrRevision = t.mrRevision
JOIN mydb2.model_from_revision_process b ON b.mrModel = a.mrModel
WHERE a.mrType = 1
ORDER BY b.iposx_model_id ASC