Basically this tag is used with select statement to find and retrieve the data from multiple tables . And this can be done with the help of join query .
suppose i have two tables , name is student and teacher then i can add the columns with the help of join query :

select student.student_id,teacher_name from teacher inner join students on teacher.teacher_id = student.teacher_id order by student_id ;<br>

Example ->
Table names -> users : user1 and user 2 , and Laptop .
Table 1 ->user1

 user_id            user_name1         
    1                 Mukesh
    2                 Shubh
    3                 Bhoomi

Table2 -> user2

user_id            user_name1         
     1               Ayush
     2               Priya
     3               Pranav

Table3 -> Laptop

Laptop_id     user_id      Laptop_name
   1               1            Lenovo
   2               2            HP
   3               L1           Asus
   4               L2           Apple

How to select data from multiple tables give below :
Query :

select L.Laptop_id , L.user_id , L.Laptop_name , u1.name1 , u2.name2 from laptop as L left join user1 as u1 on L.user_id = u1.user_id left join user2 as u2 on L.user_id = u2.user_id

Output ->

Laptop_id      user_id     Laptop_name      Laptop_name    Laptop_name
    1            1            Lenovo          Mukesh           Null
    2            2            HP              Shubh            Null
    3            3            Asus            Bhoomi           Null
    4            4            Apple           Null             Ayush