joins in sql

JOINING 2 Tables in sql

SELECT X.Column_Name , Y.Column_Name2
FROM TABLES1_NAME X 
INNER JOIN TABLES2_NAME Y ON X.Primary_key = Y.Foreign_key;


--FOR EXAMPLE
--GET THE FIRST_NAME AND JOB_TITLE
--USE EMPLOYEES AND JOBS TABLE
--THE RELATIONSHIP IS JOB_ID

SELECT E.FIRST_NAME , J.JOB_TITLE
FROM EMPLOYEES E
INNER JOIN JOBS J ON J.JOB_ID = E.JOB_ID;

SELECT Coloumn_Name(s) FROM Table_1, Table_2 WHERE Table_1.Primary_key = Table_2.Foreign_key;

SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;

SELECT *
FROM Orders
LEFT JOIN Customers
=;

 SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;
 

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.

SELECT column_name(s)

FROM table1

INNER JOIN table2
 ON table1.column_name = table2.column_name;
 

“JOIN” keyword enables us to combine two table
and get data from different tables concurrently.
Normally we can not retrieve different columns
from different tables at the same time however
Relational Database comes into picture here.
RDBMS enables us to get different data from 
different tables by mapping Primary Key and Foreign Key.
We simply tell DB that this Primary Key is
identical with that Foreign Key. So, by using
this relationship DB can combine
two different table concurently.

There are mainly four common type of join in SQL:
	1. INNER JOIN: Only some portion of the tables
    which is matching. Inner join eliminates if there is no match.
	2. FULL JOIN: All part of the tables
    both matching portions and unmatching portions from both tables.
	3. LEFT JOIN: Matching part from both
    table and unmatching part from left table.
	4. RIGHT JOIN: Matching part from both
    table and unmatching part from right table.

INNER JOIN is used when retrieving data from multiple tables and
will return only matching data.

LEFT OUTER JOIN is used when retrieving data from multiple tables and
will return left table and any matching right table records.

RIGHT OUTER JOIN is used when retrieving data from multiple tables
and will return right table and any matching left table records

FULL OUTER JOIN is used when retrieving data from multiple tables
and will return both table records, matching and non-matching.

  SELECT Orders.OrderID, Customers.CustomerName, Shippers.ShipperName
FROM 
  ((Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID)

  INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID);