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Sql Joins

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join three tables 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.

sql Join

LEFT JOIN
All rows from the left table will be returned, even if there's no matching row in the right table.

RIGHT JOIN
All rows from the right table will be returned, even if there's no matching row in the left table.

INNER JOIN
Only returns rows where there's a matching row in both tables.

sql join

SELECT columns
FROM table1 
INNER JOIN table2
ON table1.column = table2.column;
Source: www.techonthenet.com

SQL JOIN

SELECT Customers.customer_id, Customers.first_name, Orders.amount
FROM Customers
JOIN Orders
ON Customers.customer_id = Orders.customer;

sql joins explained

SELECT Employee.EmpID, Employee.EmpFname, Employee.EmpLname, Projects.ProjectID, Projects.ProjectName
FROM Employee
INNER JOIN Projects ON Employee.EmpID=Projects.EmpID;
Source: www.edureka.co

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