Try:
SELECT c.name
, c.sex
, c.address
, o.orderDATE
, c.nationality
FROM Customer c
INNER JOIN Order o
ON c.CustomerID = o.CustomerID;
But I'd change a few things.
1) Make your table name plural:
Customers
not
Customer
;
Orders
not
Order
: this reflects that the tables contain multiple items rather than a single Customer or a single Order.
2) Change
CustomerID
in your
Customers
table to just
ID
, and
OrderID
to just
ID
in your
Orders
table. You can't mix 'em up because you have to specify the table they come from Via FROM or JOIN, so why duplicate information via the column name?
Your JOIN then becomes:
ON c.ID = o.CustomerID;