Question

According to w3schools group by needs an aggregate_function(column_name).

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name

What it will happen if you commit this aggregate_function?

Thanks

Answer 1

If you are looking for best practice, do not use GROUP BY unless you are using an aggregate function. MySQL is unique in that it allows you to specify additional columns without using aggregates. This is not found in other DBMS’s.

MySQL extends the use of GROUP BY to permit selecting fields that are not mentioned in the GROUP BY clause.

The other effect that GROUP BY has is it’s sorting property.

If you use GROUP BY, output rows are sorted according to the GROUP BY columns as if you had an ORDER BY for the same columns.

If you do not include any aggregate functions, it will most likely show the DISTINCT values of the grouped column.