active record class in codeigniter (Select) Part: 1

<?php
//Get All Record From A Table
$query = $this -> db -> get('tablename');
//Produces : SELECT * FROM tablename;




//Get Record within a limit From A Table
$query = $this -> db -> get('tablename',$limit,$offset);
//Produces : SELECT * FROM `tablename` LIMIT $limit OFFSET $offset;
// LIMIT define how many row will show.
// OFFSET define after starting the execution how many row will trancat.
//For Example, in the set of alphabetic characters SELECT ... LIMIT 3 OFFSET 5 returns the characters F, G, and H


//Get Record with condition From A Table
$query = $this -> db -> get_where('tablename',array('id' => $id),$limit,$offset);
//Produces : SELECT * FROM `tablename` where id=$id LIMIT $limit OFFSET $offset;
//Note: get_where() was formerly known as getwhere(), which has been removed




//Get Permission to write the SELECT portion of query
$this -> db -> select('column_name,column_description,column_date');
$query = $this -> db -> get('tablename');
//Produces : SELECT column_name,column_description,column_date FROM tablename;
//If you are selecting all (*) from a table you do not need to use this function. When omitted, 
//CodeIgniter assumes you wish to SELECT *
//$this->db->select() accepts an optional second parameter. If you set it to FALSE, CodeIgniter will not try to protect your field or //table names with backticks. This is useful if you need a compound select statement.
//$this->db->select('(SELECT SUM(payments.amount) FROM payments WHERE payments.invoice_id=4') AS amount_paid', FALSE); 
//$query = $this->db->get('mytable');




//Get Max Value from a column From A Table
$this -> db -> select_max('column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT MAX(column_name) as column_name FROM tablename;


$this -> db -> select_max('column_name','new_column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT MAX(column_name) as new_column_name FROM tablename;




//Get Min Value from a column From A Table
$this -> db -> select_min('column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT MIN(column_name) as column_name FROM tablename;


$this -> db -> select_min('column_name','new_column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT MIN(column_name) as new_column_name FROM tablename;



//Get Average Value from a column From A Table
$this -> db -> select_avg('column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT AVG(column_name) as column_name FROM tablename;


$this -> db -> select_avg('column_name','new_column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT AVG(column_name) as new_column_name FROM tablename;



//Get Sum Value from a column From A Table
$this -> db -> select_sum('column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT SUM(column_name) as column_name FROM tablename;


$this -> db -> select_sum('column_name','new_column_name');
$query = $this -> db -> get('tablename');
//Produces : SELECT SUM(column_name) as new_column_name FROM tablename;




//Give Permission to write the from portion of your query
$this -> db -> select('column_name, column_description');
$this -> db -> from('tablename');
$query = $this -> db -> get();
//Produces : SELECT column_name, column_description FROM tablename;



//Give Permission to write the JOIN portion of your query
$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 JOIN tablename2 ON tablename2.id = tablename1.id;


$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','left');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 LEFT JOIN tablename2 ON tablename2.id = tablename1.id;


$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','right');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 RIGHT JOIN tablename2 ON tablename2.id = tablename1.id;



$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','outer');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 OUTER JOIN tablename2 ON tablename2.id = tablename1.id;




$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','inner');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 OUTER JOIN tablename2 ON tablename2.id = tablename1.id;




$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','left outer');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 LEFT OUTER JOIN tablename2 ON tablename2.id = tablename1.id;




$this -> db -> select('*');
$this -> db -> from('tablename1');
$this -> db -> join('tablename2','tablename2.id = tablename1.id','right outer');
$query = $this -> db -> get();
//Produces : SELECT * FROM tablename1 RIGHT OUTER JOIN tablename2 ON tablename2.id = tablename1.id;

?>