MySQL加入表Q.

Question

我有3个表，一个名为Doctor，Person，一个名为Appointment。他们有一个共同关系的doctor_id，但只有一个人拥有他们的Last_Name。

我需要能够生成一份医生ID列表，以及为每位医生预约的次数，无论是预约还是医生，还有医生姓名。

我如何实施医生的名字？

以下是表格：

这是我到目前为止所做的：

SELECT doctor.doctor_id, COUNT(appt_time) AS No_APP 
FROM doctor LEFT JOIN appointment ON doctor.doctor_id = appointment.doctor_id 
GROUP BY doctor.doctor_id;

Answer 1

只需为新表添加一个左连接：

SELECT doctor.doctor_id, COUNT(appt_time) AS No_APP, person.Last_name
FROM doctor LEFT JOIN appointment ON doctor.doctor_id = appointment.doctor_id 
             LEFT JOIN person on person.doctor_id = doctor.doctor_id 
GROUP BY doctor.doctor_id;

Answer 2

假设人员表包含指向医生的链接（如果需要，将在第三个表后发布时更新）

SELECT d.doctor_id, p.last_name, COUNT(a.appt_time) AS No_APP 
FROM doctor d
LEFT JOIN appointment a ON d.doctor_id = a.doctor_id
LEFT JOIN person p ON d.doctor_id = p.doctor_id
GROUP BY d.doctor_id;