从具有2列匹配mysql的3个表中获取结果

Question

I have 3 tables something like this..

Table1.
group_id        admin
................
1         x
2         y
3         z

Table2
group_id        user
....................
1               a
1               b
2               d

Table3
user            status
......................
x               hi
y               hello
z               oh
a               oho
b               sss
d               oops

now you can see that in the above tables we have group id but in the first table i have group admin and second one contains group members.. and following is the result which we want something like this in which both group admin as well as group members we want from a signle group.

group_id        user          status
....................................
1               x             hi
1               a             oho
1               b             sss

So,,,Help us to get result something like above.. in mysql

Answer 1

If you think of data in terms of data sets...

you have data in tables 1 and 2 that match in columns but you need them together. So using a UNION statement you can combine the two tables, alias the result set and join it to your third table to get the desired results.

This generates a derived table aka inline view (aliased t2)

SELECT T2.Group_ID, T2.user, T3.Status
FROM (SELECT group_ID, Admin as user 
      FROM table1
      UNION ALL
      SELECT group_ID, user 
      FROM table2
     ) t2
INNER JOIN table3 t3
 on t3.group_Id = T2.GroupID

Answer 2

Try this?

SELECT table1.group_id, table3.user, table3.status 
FROM Table1, table2
    LEFT JOIN table3 ON (table1.admin = table3.user OR table2.user = table3.user)
WHERE table1.group_id = table2.group_id AND table1.group_id = 1
GROUP BY table3.user

I am assuming every group has an admin and every user has an entry in table 3.