All for Joomla All for Webmasters

SQL JOIN

As the name shows, JOIN means to combine something. In case of SQL, JOIN means “to combine two or more tables”.

The SQL JOIN clause takes records from two or more tables in a database and combines it together.

ANSI standard SQL defines five types of JOIN :

  1. inner join,
  2. left outer join,
  3. right outer join,
  4. full outer join, and
  5. cross join.

In the process of joining, rows of both tables are combined in a single table.


Why SQL JOIN is used?

If you want to access more than one table through a select statement.

If you want to combine two or more table then SQL JOIN statement is used .it combines rows of that tables in one table and one can retrieve the information by a SELECT statement.

The joining of two or more tables is based on common field between them.

SQL INNER JOIN also known as simple join is the most common type of join.


How to use SQL join or SQL Inner Join?

Let an example to deploy SQL JOIN process:

1.Staff table

ID Staff_NAME Staff_AGE STAFF_ADDRESS Monthley_Package
1 ARYAN 22 MUMBAI 18000
2 SUSHIL 32 DELHI 20000
3 MONTY 25 MOHALI 22000
4 AMIT 20 ALLAHABAD 12000

2.Payment table

Payment_ID DATE Staff_ID AMOUNT
101 30/12/2009 1 3000.00
102 22/02/2010 3 2500.00
103 23/02/2010 4 3500.00

So if you follow this JOIN statement to join these two tables ?

  1. SELECT Staff_ID, Staff_NAME, Staff_AGE, AMOUNT
  2.    FROM STAFF s, PAYMENT p
  3.    WHERE s.ID =p.STAFF_ID;

This will produce the result like this:

STAFF_ID NAME Staff_AGE AMOUNT
3 MONTY 25 2500
1 ARYAN 22 3000
4 AMIT 25 3500
1 ARYAN 22 3000
PinIt
submit to reddit

Leave a Reply

Top