Db pattern for finding the owner of a record - mysql

Question

I'm looking for a pattern for dealing with a situation where a record in a table may be related to 1 and only one of several other records and I need to know which. It's difficult to describe so I will use an example with an oauth client from a recent project.
A client has an id and secret and teams or users may own clients
clients
client_id|client_secret
user_clients
user_id|client_id
team_clients
team_id|client_id
The issue here is when someone attempts to use client credentials to get an access token I need to know if those credentials belong to a team or a user. I'm not really sure of the best way to deal with this, I control the database so changes can be made.
Some options I've considered:
Modify clients and remove user_clients and team clients
clients
client_id|client_secret|team_id(nullable)|user_id(nullable)
Create a client owners table and remove user_clients and team_clients
client_owners
team_id(nullable)|user_id(nullable)|client_id
Adding a type to the clients table and doing 2 queries or a conditional query
clients
client_id|client_secret|type(user or team)
Left joins and filtering/mapping in code.
select * from clients c left join user_clients u ... left join team_clients t ... where c.client_id = ?
None of these options feel great so I am wondering if there is a better pattern. This is a simplified example, sometimes these objects are much more complicated and have many more possible relationships so the queries can get pretty hairy and also difficult to manage when using an orm (though requiring raw sql for parts of the system is not an issue).
I'd love to hear how people are solving this problem.
Thanks in advance.

Answer 1

Design
What you describe are 1:n relations:
One user can own multiple clients
One team can own multiple clients
So, the first approach seams appropriate: The client table has a user column and a client column.
Now you say a client can only be owned by either a user or a client. You would have a check contraint on the client table for this to ensure that only one of the IDs is set. (And if every client must have an owner, this constraint would also care about this.)
Some example queries
If you want to get all clients owned by users:
select * from clients where user_id is not null;
If you want to know whether a client is owned by a user or a team:
select
c.*,
case when user_id is not null then 'user'
when team_id is not null then 'team'
else 'none'
end as owner
from clients c;
If you want user or team information:
select c.*, coalesce(u.name, t.name) as owner_name
from clients c
left join users u on u.user_id = c.user_id
left join teams t on t.team_id = c.team_id;

Answer 2

The idea with the left joins is something you can go with. Leave your clients table with just clientID and left join it on user_clients and team_clients.
You could also combine that with your first option and add a column for user_clientsID and team_clientsID and at adding to the left join clients.user_clientsID <> 0 which is going to help you with the.
The 2nd and 3rd option is something I have seen used as well. With the second option perhaps being the one that can sometimes create the most headaches.
Also an option you can consider is creating a view table with all the information you might need