根据架构查找在MySQL中拥有汽车的总人数

Question

嘿伙计们我正在做一些考试修改,并通过过去的论文可以有人告诉我,如果我在正确的轨道上.

考虑下面给出的保险数据库:

person (driver-id, name, address)<br>
car (license, model, year)<br>
accident (report-number, date, location)<br>
owns (driver-id, license) <br>
participated (driver-id, car, report-number, damage-amount)<br>

1)查找2004年拥有涉及事故的汽车的总人数.

这是我想出的:

SELECT COUNT(driver-id)
FROM participated
WHERE participated.reportnumber=accident.reportnumber
AND accident.date = 2004

我是在正确的轨道上吗？任何帮助,将不胜感激.

Answer 1

不,这不对,你必须参考accident表格:

SELECT COUNT(`driver-id`)
FROM participated
INNER JOIN accident ON  participated.reportnumber = accident.reportnumber
WHERE accident.date = 2004