Объединить 3 таблицы в sql t1-student(s_id, s_name) t2-marks(school_id, s_id,score,status) t3-details(address_city,email_id,school_id) t4-output(s_name,score,status, address_city, email_id)

объединение трех таблиц sql

Suppose we are having three table named as 
Student_details
Attendance_details
Batch_details
And we have to apply join these three tables for fetching records

Example query:
select column_names
from Student_detail as s join Attendance_details as a on
s.s_id = a.s_id join Batch_details as b on 
s.s_id = b.s_id;

Here in the above example we implemented simple join but you change it with own join requirements.