mysql - what is the difference between GROUP BY and ORDER BY in sql

Question

When do you use which in general? Examples are highly encouraged!

I am referring so MySql, but can't imagine the concept being different on another DBMS

Answer 1

ORDER BY alters the order in which items are returned.

GROUP BY will aggregate records by the specified columns which allows you to perform aggregation functions on non-grouped columns (such as SUM, COUNT, AVG, etc).

TABLE:
ID NAME
1  Peter
2  John
3  Greg
4  Peter

SELECT *
FROM TABLE
ORDER BY NAME

= 
3 Greg
2 John
1 Peter
4 Peter

SELECT Count(ID), NAME
FROM TABLE
GROUP BY NAME

= 
1 Greg
1 John 
2 Peter

SELECT NAME
FROM TABLE
GROUP BY NAME
HAVING Count(ID) > 1

=
Peter