Check out example codes for "group by in mysql". It will help you in understanding the concepts better.

Code Example 1

SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders 
FROM Orders
LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID
GROUP BY ShipperName;

Code Example 2

# Say you have a table called SALARIES that contains a 
# few duplicate NAME entries...
+----+-------------+--------+
| ID |    NAME     | SALARY |
+----+-------------+--------+
| 1	 |     Bob     |  500   |
| 2  |    Alice    |  500   |
| 3  |    Alice    |  200   |
| 4  |    Frank    |  700   |
| 5  |    Percy    |  100   |
| 6  |    Percy    |  800   |
| 7  |   Cyrille   |  400   |
+----+-------------+--------+

# We can obtain the total salaries of each person
# by using GROUP BY in the following query...
SELECT NAME, SALARY FROM SALARIES GROUP BY NAME;

# Which will output the following...
+------------+--------+
|   Alice    |  700   |
|    Bob     |  500   |
|  Cyrille   |  400   |
|   Frank    |  700   |
|   Percy    |  900   |
+------------+--------+

Code Example 3

SELECT column_name(s)
  FROM table_name
  WHERE condition
  GROUP BY column_name(s)
  HAVING condition
  ORDER BY column_name(s);

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