All columns in the SELECT clause that do not have an aggregate need to be in the GROUP BY
Good:
SELECT col1, col2, col3, MAX(col4)
...
GROUP BY col1, col2, col3
Also good:
SELECT col1, col2, col3, MAX(col4)
...
GROUP BY col1, col2, col3, col5, col6
No other columns = no GROUP BY needed
SELECT MAX(col4)
...
Won’t work:
SELECT col1, col2, col3, MAX(col4)
...
GROUP BY col1, col2
Pointless:
SELECT col1, col2, col3, MAX(col4)
...
GROUP BY col1, col2, col3, MAX(col4)
Having an aggregate (MAX etc) with other columns without a GROUP BY makes no sense because the query becomes ambiguous.