Операторы LEFT OUTER JOIN и RIGHT OUTER JOIN.
Задача

Question

Выгрузи таблицу из двух полей: первое поле с фамилией сотрудника, второе — с количеством пользователей, чьи запросы этот сотрудник обработал. Назови поля employee_last_name и all_customers соответственно. Сгруппируй записи по идентификатору сотрудника. Отсортируй количество пользователей по убыванию.
SELECT e.last_name AS employee_last_name, 
       COUNT(c.customer_id) AS all_customers 
FROM employee AS e 
INNER JOIN customer AS c ON e.employee_id =  
c.support
 _rep_id 
GROUP BY e.employee_id, e.last_name 
ORDER BY all_customers DESC; 
- не работает!
SELECT s.last_name AS employee_last_name, 
       COUNT(c.customer_id) AS all_customers 
FROM staff AS s 
LEFT OUTER JOIN client AS c ON s.employee_id =  
c.support
 _rep_id 
GROUP BY s.employee_id 
ORDER BY all_customers DESC, employee_last_name;
-не работает

z9xsvoipgjphzyl · Accepted Answer

SELECT e.last_name AS employee_last_name,  &#10;       COUNT(c.customer_id) AS all_customers  &#10;FROM employee AS e  &#10;LEFT OUTER JOIN customer AS c ON e.employee_id = c.support_rep_id  &#10;GROUP BY e.employee_id, e.last_name  &#10;ORDER BY all_customers DESC, employee_last_name; &#10; 
 SELECT e.last_name AS employee_last_name,  &#10;       COUNT(c.customer_id) AS all_customers  &#10;FROM employee AS e  &#10;RIGHT OUTER JOIN customer AS c ON e.employee_id = c.support_rep_id  &#10;GROUP BY e.employee_id, e.last_name  &#10;ORDER BY all_customers DESC, employee_last_name; &#10;

Операторы LEFT OUTER JOIN и RIGHT OUTER JOIN. Задача