function example_customizer( $wp_customize ) {

$wp_customize->add_section(
'example_section_one',
array(
    'title' => 'Example Settings',
    'description' => 'This is a settings section.',
    'priority' => 35,
)
);

$wp_customize->add_setting(
'select_revslider',
array(
'default' => 'wordpress',
)
);


$wp_customize->add_control(
'select_revslider',
array(
'type' => 'select',
'label' => 'Please Select a Slider:',
'section' => 'example_section_one',
'choices' => array(
    'wordpress' => 'WordPress',
 ),
 )
 );

<?php

global $wpdb; //Accessing WP Database (non-WP Table) use code below.

$results = $wpdb->get_results('SELECT alias FROM wp_revslider_sliders');

foreach ($results as $result) {
$revchoices = array("text" => $result, "value" => $result);
}

return $revchoices;

?>

$wp_customize->add_control(
    'select_revslider',
array(
    'type' => 'select',
    'label' => 'Please Select a Slider:',
    'section' => 'example_section_one',
    'choices' => include('jktestrev.php'),
)
);