SQL '08: How to count all sku's in one table not found in another table

I would like to do something similar to this psuedo-SQL:

开发者_开发知识库SELECT COUNT(A.SKU) 
  FROM TableA as A
 WHERE a.sku NOT IN TableB

Multiple solutions, example with EXISTS :

SELECT COUNT(A.SKU) AS your_count
FROM TableA
WHERE NOT EXISTS(SELECT NULL
                 FROM TableB
                 WHERE B.SKU = A.SKU);

You could also use EXCEPT :

SELECT COUNT(*)
FROM (
    SELECT SKU
    FROM TableA
    EXCEPT
    SELECT SKU
    FROM TableB);

You could also use NOT IN, LEFT OUTER JOIN ... WHERE B.SKU IS NULL, etc.