using get_var
example:
$table_name = $wpdb->prefix . "posts";
$post_content = $wpdb->get_var($wpdb->prepare( "SELECT post_content FROM $table_name WHERE post_status = %s",'publish'));
echo $post_content;
example:
$table_name = $wpdb->prefix . "posts";
$post_content = $wpdb->get_var($wpdb->prepare( "SELECT post_content FROM $table_name WHERE post_status = %s",'publish'));
echo $post_content;