JOIN in SQL combines records from 2 tables in a database. Often we might need to extract daata from 2 or more tables and then we need Joins. It simply is an act of joining 2 or more tables in a single temporary table.

Example:

DepartmentTable

EmployeeTable

Assume we have 2 tables as mentioned above. And we need to list people in each department. We can do this using a simple Join as follows:

"Select EmployeeTable.EmployeeName, DepartmentTable.DepartmentName from EmployeeTable, DepartmentTable where EmployeeTable.DepartmentId = DepartmentTable.DepartmentId";

This is a "simple join" that fetches results from 2 tables and display it. The result is:

The Code in PHP for the same would be :

<?php
// Make a MySQL Connection
// Construct our join query
$query = "Select EmployeeTable.EmployeeName,  DepartmentTable.DepartmentName from EmployeeTable, DepartmentTable where EmployeeTable.DepartmentId = DepartmentTable.DepartmentId";
	 
$result = mysql_query($query) or die(mysql_error());


// Print out the contents of each row into a table 
while($row = mysql_fetch_array($result)){
	echo $row['EmployeeName']. " - ". $row['DepartmentName'];
	echo "<br />";
}
?>

This was a simple join used to fetch and display result from 2 tables. We'll now move to LEFT and Other Joins.