MySQL：根据用户联接四个表

Question

After spending few hours yesterday, I decided to post here. I have a database with few tables and I need to join 4 tables based on users table's idusers (id of user).

Four tables that needs to be joined are: users, table1, table2 and table3.

users
idusers, name, email, a, b, c, etc.

table1 
custom_id1, a_id, users_idusers

table2 
custom_id2, a_id, users_idusers, comment

table3 
custom_id3, lang

How they are related: - User signs up and the data is stored to users table: I need all fields from this table. - When they take an action, it gets stored in table1 (where users_idusers is users.idusers). - Some actions (with comment) register to table2 (users_idusers is users.idusers). - table1 and table2's a_id field is same and mapped to table3's custom_id3.

What I need: I want to be able to get all actions from table1 mapped to its user from the user table, table3 for lang and table2 (if there is a comment, get the text or return null for that field.).

What my query looks like:

SELECT table1.a_id, table1.users_idusers, users.*, table3.langkey
    FROM table1
    LEFT JOIN users ON (users.idusers = table1.users_idusers)
    LEFT JOIN table3 ON (table1.a_id = table3.custom_id3);

The query above is missing the part that needs to join table2 and that's where I'm stuck. Any help would be appreciated.

Thank you.

Answer 1

SELECT u.*
     , and
     , some
     , other
     , columns
  FROM users u
  JOIN table1 a
    ON a.users_idusers = u.idusers
  JOIN table3 l
    ON l.custom_id3 = a.a_id
  LEFT
  JOIN table2 c
    ON c.a_id = a.a_id
  [AND c.users_idusers = a.users_idusers]??