Newbie Question

Table 1
Order Number
1234
4321
5601
Table 2
Order Number
1234
4321
How do I Get SQL to Return that the Order number 5601 does not match any Order number in Table 2:Try:

SELECT Table1.OrderNumber
FROM Table1 LEFT JOIN Table2 ON Table1.OrderNumber = Table2.OrderNumber
WHERE Table2.OrderNumber Is Null