dbDelta sample

setup-database.php

<?php
global $wpdb;
require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );  

$sql = "CREATE TABLE `{$wpdb->prefix}app_employees` (
            `id` INT(11) NOT NULL AUTO_INCREMENT,
            `post_id` BIGINT(20) DEFAULT NULL,
      `emp_number` VARCHAR(20) COLLATE {$wpdb->collate} DEFAULT NULL, 
      `full_name` VARCHAR(100) COLLATE {$wpdb->collate} DEFAULT NULL, 
      `gender` VARCHAR(6) COLLATE {$wpdb->collate} DEFAULT NULL, 
      `birth_date` DATE DEFAULT NULL, 
      `email` VARCHAR(200) COLLATE {$wpdb->collate} DEFAULT NULL, 
      `mobile` VARCHAR(20) COLLATE {$wpdb->collate} DEFAULT NULL, 
      `join_date` DATE DEFAULT NULL, 
      `empfunction_id` INT(11) DEFAULT NULL,
      `empfunction_date` DATE DEFAULT NULL,
            `user_id` BIGINT(20) DEFAULT NULL,
            `date_trashed` DATETIME DEFAULT NULL,
            PRIMARY KEY (`id`)
        ) ENGINE=InnoDB COLLATE={$wpdb->collate}; ";

dbDelta( $sql );