How to create a Custom Module for autocomplete form element article in Drupal 7

module.php 
<?php
/**
* Implements hook_menu.
*/
function module_name_menu() {
$items['ajaxform_autocomplete_callback'] = array(
 'page callback' => 'ajaxform_autocomplete_callback',
 'type' => MENU_CALLBACK,
 'access callback' => TRUE,
);
return $items;
}
/**
* Create Form.
*/
function module_name_form($form, &$form_state){
$form['article_search'] = array(
 '#type' => 'textfield',
 '#title' => 'Search Article',
 '#maxlength' => 128,
 '#autocomplete_path' => 'ajaxform_autocomplete_callback',
);   
return $form;
}

function ajaxform_autocomplete_callback($text) {
$matches = array();
     $items = db_query_range('SELECT n.nid, n.title, n.created FROM {node} n WHERE n.title LIKE :string', 0, 10, array('string'=>'%' . db_like($text). '%'));
 foreach ($items as $item) {
      $matches[$item->title] = $item->title . '( nid: ' . $item->nid .')';
       }
       drupal_json_output($matches);
}
?>
Output:- 

Way2:- How to fetch the data in particular table using custom code in drupal 7
step 1:- We have a table and the table name is like 'Curd' we have some data in a table like:-

step 2:- Fetch the data in table Curd

Now Full code retrieve the data article and curd table... 
module.php
<?php
/**
* Implements hook_menu.
*/
function module_name_menu() {
$items['ajaxform_autocomplete_callback'] = array(
 'page callback' => 'ajaxform_autocomplete_callback',
 'type' => MENU_CALLBACK,
 'access callback' => TRUE,
);
return $items;
}
/**
* Create Form.
*/
function module_name_form($form, &$form_state){
$form['article_search'] = array(
 '#type' => 'textfield',
 '#title' => 'Search Article',
 '#maxlength' => 128,
 '#autocomplete_path' => 'ajaxform_autocomplete_callback',
);   
return $form;
}

function ajaxform_autocomplete_callback($text) {
Use any of one code

1.Article data retrieve

$matches = array();
     $items = db_query_range('SELECT n.nid, n.title, n.created FROM {node} n WHERE n.title LIKE :string', 0, 10, array('string'=>'%' . db_like($text). '%'));

 foreach ($items as $item) {
      $matches[$item->title] = $item->title . '( nid: ' . $item->nid .')';
       }
       drupal_json_output($matches);

2.This code use for custom table data retrieve
     
       $results = array();
       $query = db_select('curd', 'c');
       $query
        ->condition('c.coupon_name', '%' . db_like($text) . '%', 'LIKE')
        ->fields('c', array('coupon_name'))
        ->orderBy('coupon_name', 'ASC');
       $colors = $query->execute();
     
       foreach ($colors as $row) {
      $results[$row->coupon_name] = check_plain($row->coupon_name);
       }
     drupal_json_output($results);
}
?>