mysql> SELECT avg(UnitPrice)
    -> FROM order_details;
+----------------+
| avg(UnitPrice) |
+----------------+
|    26.21851972 | 
+----------------+
1 row in set (0.00 sec)

mysql> SELECT avg(UnitPrice) AS 'Przecietna cena'
    -> FROM order_details;
+-----------------+
| Przecietna cena |
+-----------------+
|     26.21851972 | 
+-----------------+
1 row in set (0.00 sec)
