Question

okay I have some table like this..

table TopicForum
-------------------------
 - idforum (PK)
 - iduser (FK)
 - subject
 - content


table Usermember
--------------------------------
-iduser (PK)
-password
-accesslevel

table student
-------------------------------
-idstudent (PK)
-iduser (FK)
-name

table teacher
---------------------------------
-idtecher (PK)
-iduser(FK)
-name

table admin
-----------------------------------
-idadmin (PK)
-iduser(FK)
-name

so I want show name in TopicForum reference by iduser in student , teacher, and admin..

please help thanks

Answer 1

Try this:

SELECT DISTINCT A.name, A.iduser 
FROM (SELECT NAME, iduser FROM Student
      UNION 
      SELECT NAME, iduser FROM Teacher
      UNION
      SELECT NAME, iduser FROM Admin) AS A 
INNER JOIN TopicForum tf ON A.iduser = tf.iduser