Create database on plugin activation hook

plugins.php

<?php
register_activation_hook( __FILE__, 'plugin_create_db' );
function plugin_create_db() {
    // Create DB Here
    global $wpdb;
    $charset_collate = $wpdb->get_charset_collate();
    $table_name = $wpdb->prefix . 'test_table';

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        another_ID varchar(255) default NULL,
        first_name varchar(255) default NULL,
        import_time datetime NOT NULL default '0000-00-00 00:00:00',
        import_timestamp longtext,
        PRIMARY KEY (id),
        UNIQUE KEY(another_ID)
    ) $charset_collate;";

    // is_inserted_wp_users is to check for if is users is inserted with wp_insert_user

    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );
}