The code is as below:

/**
* display the data.
*/
function display_data($form, &$form_state) {
//Use Database API to retrieve records.
$query = db_select(‘info_manager’, ‘n’)
->fields(‘n’, array(‘id’, ‘first_name’, ‘last_name’, ’email’))
->orderBy(‘id’, ‘DESC’); //Most recent first.
$result = $query->execute();

//Iterate over the resultset and format them.
$header = array(‘ID’, ‘First Name’, ‘Last Name’, ‘Email’);
$rows = array();
foreach ($result as $row){
$rows[] = array($row->id,
$row->fist_name,
$row->last_name,
$row->email,
);
}

if (empty($rows)) { //No content in the last week.
$page_array[‘info_manager_arguments’] = array(
//Title serves as page subtitle
‘#title’ => t(‘All posts from the last week’),
‘#markup’ => t(‘No posts available.’),
);
return $page_array;
}
else {
$page_array[‘info_manager_arguments’] = array(
‘#header’ => $header,
‘#rows’ => $rows,
//Theme function includes theme hook suggestion.
‘#theme’ => ‘table__info_manager’,
);
return $page_array;
}
}

helpful links:

Default theme implementations
https://api.drupal.org/api/drupal/modules!system!theme.api.php/group/themeable/7

Drupal for Beginners: How to Create a Table Using theme_table()
http://zgadzaj.com/drupal-for-beginners-how-to-create-a-table-using-themetable

Below is from drupal.org

The hook will only be called the first time a module is enabled or after it is re-enabled after being uninstalled.

Generally, the “uninstalled” can be ignored. On the module page, there is a tag named “uninstall” on the top-right corner. Click to open, then the modules are listed there. check the space before the module you want to uninstall, then click “uninstall” button to uninstall.

Change the int type to serial.

The below is an example:

function info_manager_schema() {
$schema = array();
$schema[‘info_manager’] = array(
// specification for  table info_manager
‘fields’ => array(
‘id’ => array(
‘description’ => t(‘The primary identifier for a record.’),
‘type’ => ‘serial’,
‘unsigned’ => TRUE,
‘not null’ => TRUE,),
‘first_name’ => array(
‘description’ => t(‘The first name of the contact.’),
‘type’ => ‘varchar’,
‘length’ => 255,),
‘last_name’ => array(
‘description’ => t(‘The last name of the contact.’),
‘type’ => ‘varchar’,
‘length’ => 255,),
’email’ => array(
‘description’ => t(‘The email of the contact.’),
‘type’ => ‘varchar’,
‘length’ => 255,),
),
‘primary key’ => array(‘id’),
);
return $schema;
}