def bestellen(dic, customerid):
    conn = pg.connect(host=HOST, database=DATABASE, user=USER, password=PW)
    curs = conn.cursor()
    curs.execute("BEGIN")
    wheres = []
    for key in dic:
        wheres.append("prod_id = " + str(key) + " ")

    curs.execute("SELECT * FROM inventory WHERE " + "OR ".join(wheres) + "FOR UPDATE")

    # überprüft ob noch genug Artikel vorhanden sind
    curs.execute("SELECT prod_id, quan_in_stock FROM inventory WHERE " + "OR ".join(wheres))
    for x in curs.fetchall():
        if not int(dic[x[0]]) <= int(x[1]):
            return False

    g = 0
    try:
        for key in dic:
            # quan_in_stock = quan_in_stock - (ausgewählte Anzahl an Produkten)
            curs.execute("UPDATE inventory SET quan_in_stock = (SELECT quan_in_stock FROM inventory WHERE prod_id = " + str(key) + ") - " + str(dic[key]) + " WHERE prod_id = " + str(key))
            # sales = sales + (ausgewählte Anzahl an Produkten)
            curs.execute("UPDATE inventory SET sales = (SELECT sales FROM inventory WHERE prod_id = " + str(key) + ") + " + str(dic[key]) + " WHERE prod_id = " + str(key))

            # von jedem key * Anzahl: Preis berechnen
            curs.execute("SELECT price FROM products WHERE prod_id = " + str(key))
            g += curs.fetchone()[0] * dic[key]

        # nächst höhere orderid bestimmen
        curs.execute("SELECT max(orderid) FROM orders")
        orderid = str(int(curs.fetchone()[0]) + 1)
        netamount = (float(g)/100.)*(100-TAX)
        tax = (float(g)/100.)*TAX

        # new order
        curs.execute("INSERT INTO orders VALUES(" + str(orderid) + ", (SELECT CURRENT_DATE), " + str(customerid) + ", " + str(netamount) + ", " + str(tax) + ", " + str(g) + ")")
        # cust_hist/ orderlines erweitern
        orderlineid = 1
        for key in dic:
            curs.execute("INSERT INTO cust_hist VALUES(" + str(customerid) + ", " + orderid + ", " + str(key) + ")")
            curs.execute("INSERT INTO orderlines VALUES(" + str(orderlineid) + ", " + orderid + ", " + str(key) + ", " + str(dic[key]) + ", (SELECT CURRENT_DATE))")
            orderlineid += 1
        conn.commit()
    except pg.DatabaseError:
        conn.rollback()
        bestellen(dic, customerid)
    return True