Many to Many Relationship using Joins - mysql

Question

I have a database two tables and a linking table that I need a JOIN query for:
Here are my Tables:
family (userid (int), loginName, etc)
member (memberid (int), loginName(this links member to a family),name, etc)
Linking Table:
user2member (userid,memberid)...would both be foreign keys?
I want to do two things:
1) Be able to have a family.loginName(12,Johnson) subscribe to another family.loginName (43,Smith) and record that into the linking table.
That would look like this:
12,43
2) When I do a query for all the member.name that are in the Johnson Family, I'll get all the Johnsons & all the Smiths.
If Johnson = Ted, Sue & Patty
IF Smith =Joe, Sue & Bob
my query results would be Johnson now = Ted,Sue,Patty,Joe,Sue,Bob
I asked this question a few days ago without good table names and I ended up confusing myself and the nice guy Ollie Jones who posted an answer similar to this for the query:
SELECT member.name
FROM family
JOIN user2member on family.userid = member.memberid
JOIN member on user2member.name = member.name
 WHERE family.userid = '30'
ORDER BY member.name
I had to change Ollie's answer to match my tables but I'm getting a limit error 0,30 on line 5.
This is my first time doing JOINS and I have no idea if this is correct.
Thanks,
Here's the link to my first question: mySQL table linking , group linked to other members lists, the displaying all members

Answer 1

I am not sure, if the tables you suggested would solve your problem. If I understand your question correct, there are two relationships:
a relationship for all family members (Johnson with Ted, Sue, Patty, Smith with Joe, Sue, Bob)
a relationship for subscriptions (a family can subscribe to another family)
I would suggest following tables:
family (f_id, f_loginName, etc.)
member (m_id, m_f_id, m_name) (foreign key to family, many-to-one relationship)
subscription (s_f_id,s_to_f_id) (linking is based on both family keys)
This would result in following contents:
family:
f_id f_loginName
12 Johnson
43 Smith
member:
m_id m_f_id m_name
1 12 Ted
2 12 Sue
3 12 Patty
4 43 Joe
5 43 Sue
6 43 Bob
subscription
s_f_id s_to_f_id
12 43
Now, to get all possible members for a specific family and it's subscriptions, I would use following SQL query. It has a simple join for family and it's family members. In the WHERE clause, the family Johnson is fetched (f_id = 12) and to get all family members from the subscriptions, it's easier to use a subquery.
SELECT f_loginName, m_name
FROM family
INNER JOIN member ON m_f_id = f_id
WHERE f_id = 12
OR f_id IN (SELECT s_to_f_id FROM subscription WHERE s_f_id = 12)
ORDER BY f_loginName, m_name;