Probable cause

You used a non-aggregate function or column reference in the select list or in a nested query block that does not appear in the GROUP BY clause. In a query using GROUP BY, select list items that are not aggregate functions must also appear in the GROUP BY clause. If the select list item is a column reference or an alias, you may add the column name or alias to the GROUP BY clause. If the select list item is a scalar function, ensure that the function's arguments in the GROUP BY clause match exactly with those in the select list. In some cases, you may want to use the MAX function on the column name (or another aggregate function) instead of adding the column to the GROUP BY clause.