thinkphp three table related query, how to solve

thinkphp Three-Table association query
Three tables, R_hospital table r_department table R_doctor table
ID ID hospital_id ID depart_id hospital_id
The three tables belong to the relationship as above,
Two table associations: I Will,
$condition [' hospital_id '] = $data;
Passing query criteria into Query method
$result = $room->join (' r_hospital on R_department.hospital_id=r_hospital.id ')->where ($condition)->select ( );
Find three Table association statements?

$result = $room->join (' left join R_hospital in R_department.hospital_id=r_hospital.id left join doctor on doctor.id = X X.id ')->where ($condition)->select (); I don't know what's wrong with this statement.

------Solution--------------------
can always jion down
------Solution--------------------
You first clear the main foreign key relationship of the table, and then write the SQL

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