multi-table mysql query
looks like you need to use "join" syntax. Something like:

SELECT 
u.name,
u.id,
m.id,
t.id,
p.id,
FROM User u
LEFT JOIN Message m ON m.owner_user_id = u.id
LEFT JOIN Thread  t ON t.owner_user_id = u.id
LEFT JOIN Project p ON p.owner_user_id = u.id
WHERE u.id = 12345


Of course, this will have to be modified to include the fields you actually want returned and whatever sorting and ordering you may want... but this should get you started. Good luck!