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>
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
user_id user_name1
1 Mukesh
2 Shubh
3 Bhoomi
Table2 -> user2
- user_id user_name1
- 1 Ayush
- 2 Priya
- 3 Pranav
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
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
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
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
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