Question

我列出了他们的职业列表如下：

Doctor Male
Teacher  Male
Principal Male
Nurse Female
Doctor Male

当我按职业分组时，我希望Access为任何不在我所拥有的子列表中的职业返回0。这是我正在使用的代码：

SELECT Profession.Profession, Count(Profession.Profession) AS CountOfProfession
FROM People INNER JOIN Profession ON People.PeopleID = Profession.PeopleID
WHERE (((People.Sex)="Male"))
GROUP BY Profession.Profession;

我希望它能为医生提供2，因为有2名男性，但由于没有男护士，因此护士也会收0。请让我知道如何做到这一点，谢谢！

Answer 1

您需要外部联接。我改变了表的顺序，因此它是left join：

SELECT Profession.Profession,
       sum(iif(people.sex = "Male", 1, 0)) AS CountOfProfession
FROM Profession LEFT JOIN
     ON People.PeopleID = Profession.PeopleID 
GROUP BY Profession.Profession;

Answer 2

这可以通过外连接并将条件从WHERE移动到ON子句来完成：

SELECT Profession.Profession, 
       COUNT(People.PeopleID) AS CountOfProfession
FROM Profession 
  LEFT JOIN People 
    ON (  People.PeopleID = Profession.PeopleID
      AND People.Sex = 'Male' )
GROUP BY Profession.Profession ;

SQL - 使用Count时为0

2 个答案: