sql - 计数，内连接

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，我需要找出责任是“是”的事故是由哪个司机参与的，以及发生了多少次。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（我想使用内部连接）。我不知道怎么做，因为它既不包含在聚合函数也不包含在 GROUP BY 子句中。请帮忙 ：）

Answer 1

正如您所怀疑的，您需要使用内部联接。由于名字和姓氏现在是 SELECT 的一部分，因此您还需要在 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

应该管用。