伯爵，内联

Question

我有两张桌子：

DRIVER(Driver_Id,First name,Last name,...);

PARTICIPANT IN CAR ACCIDENT(Participant_Id,Driver_Id-foreign key,responsibility-yes or no,...).

现在，我需要找出哪个司机参与了事故，责任是'是'，以及多少次。我这样做了：

Select Driver_ID, COUNT (Participant.Driver_ID)as 'Number of accidents'
from Participant in car accident
where responsibility='YES'
group by Driver_ID
order by COUNT (Participant.Driver_ID) desc 

但是，我需要从第一个表中添加驱动程序的名字和姓氏（我猜想使用内部联接）。我不知道如何，因为它不包含在聚合函数或GROUP BY子句中。 请帮助：）

Answer 1

如您所料，您需要使用内部联接。并且因为名字和姓氏现在是SELECT的一部分，所以您还需要在GROUP BY中包含这些列。

Select Driver_ID, First_name, Last_name COUNT (Participant.Driver_ID) as "Number of accidents"
from "Participant in car accident" join Driver on "Participant in car accident".Driver_ID = Driver.Driver_ID
where responsibility='YES'
group by Driver_ID, First_name, Last_name
order by COUNT (Participant.Driver_ID) desc

这是家庭作业吗？

Answer 2

您可以使用内联表：

SELECT d.driver_first_name,
       d.driver_last_name,
       r.incident_count
FROM  DRIVER d
INNER JOIN (SELECT driver_id, 
                   count(*) incident_count
            FROM PARTICIPANT_IN_CAR_ACCIDENT
            WHERE responsibility = 'YES'
            GROUP BY driver_id) r
    ON d.driver_id = r.driver_id
ORDER BY r.incident_count DESC

应该工作。