mysql – sql query average sum

Question:

Please help me write a sql query to display the average amount for each employee for all orders. Example:

Первая табличка
ID_работника Фамилия
1            Иванов
2            Петров
3            Соколов
4            Сидоров

Вторая табличка
номер заказа ID_работника date_time                Сумма
1            2            2016-09-13 17:06:43.617  10
2            2            2016-09-13 17:06:43.617  20
3            4            2016-09-13 17:06:43.617  25

Answer:

SELECT 
     t1.ID_работника
    ,AVG(t2.Сумма)
FROM [Первая табличка] AS t1
     INNER JOIN [Вторая табличка] AS t2 ON t1.ID_работника = t2.ID_работника
GROUP BY t1.ID_работника

PS Cyrillic EVIL!!! Learn English.