mysql - 进行mysql查询以从某个表中查找所有人

Question

假设我有一张桌子Person，我还有另外 3 Doctor, Policeman, Lawyer.... 这 3 张桌子idPerson从中获取共同的属性，如姓名 surname 等.... 如果我想找到所有医生或律师的人他们从表中的共同信息Person，我该怎么做？

我尝试过类似的东西（通过将所有组合右连接，左连接，内连接来播放）

SELECT Person.* 
FROM Person 
RIGHT JOIN doctor ON doctor.idPerson = person.idPerson 
LEFT JOIN lawyer ON lawyer.idPerson = person.idPerson

Answer 1

除了使用连接之外，您可能会发现使用起来更简单EXISTS：

SELECT col1, col2, ... coln
FROM Person
WHERE EXISTS (
    SELECT * FROM Doctor WHERE Doctor.idPerson = Person.idPerson
) OR EXISTS (
    SELECT * FROM Lawyer WHERE Lawyer.idPerson = Person.idPerson
) 

Answer 2

试试这个

SELECT Person.* 
FROM Person 
LEFT JOIN doctor ON doctor.idPerson = person.idPerson 
LEFT JOIN lawyer ON lawyer.idPerson = person.idPerson
WHERE lawyer.idPerson IS NOT NULL 
OR doctor.idPerson IS NOT NULL 

Answer 3

SELECT Person.* FROM Person 
left outer JOIN doctor ON doctor.idPerson = person.idPerson 
LEFT outer JOIN lawyer ON lawyer.idPerson = person.idPerson
where doctor.personid is not null
or laywer.personid is not null