Question

我在MySQL DB中有三个表

表1包含以下字段

Name of Table: SupervisorTable 
supervisorid (autoinc, bigint) 
employeeid (bigint) //same as User.userid
supervisorname

Name of Table: User 
userid (autoinc, bigint) 
userFullName (string) 
supervisorid (bigint) 
divisionid (bigint)

Name of Table: DivisionTable 
divisionid(autoinc, bigint) 
divisionname (string)

我希望能够确定主管在哪个部门工作，我的输出应该是主管姓名和部门名称。我的最新尝试：

SELECT supervisortable.supervisorname,
       divisiontable.divisionname 
  FROM supervisortable, 
       user, 
       divisiontable 
 WHERE supervisortable.employeeid = user.userid;

这给了每个部门的主管姓名的每个组合：

supervisorname  divisionname
----------------------------
UserA           Department1
UserB           Department1
UserA           Department2
...
UserB           DepartmentN

Answer 1

如果您想查找查找所有主管的查询并在OP中列出所需的输出，那么这样做：

SELECT S.supervisorname,
       D.divisionname
  FROM SuperisorTable S
  JOIN User U ON S.employeeid= U.supervisorid
  JOIN DivisionTable D ON U.divisionid = D.divisionid

因为没有标准，你会得到一个笛卡尔积（这很糟糕，除非你真的想要那个）。

Answer 2

SELECT s.supervisorname, d.divisionname
FROM DivisionTable d, SupervisorTable s, User u
WHERE d.divisionid =  u.divisionid
AND s.supervisorid = u.supervisorid
AND s.employeeid = u.userid

Answer 3

我正确理解您的数据结构：

SELECT 
  S.supervisorname,        
  D.divisionname 
FROM SuperisorTable S  
INNER JOIN Users U ON S.employeeid = U.userid  
INNER JOIN DivisionTable D ON U.divisionid = D.divisionid

关于SQL查询的问题

3 个答案: