Update/Insert Records If Not Exist

[Guest]

I have two table; TableA and TableB having the same structure. TableB has
some records that do not exist in TableA. How do I write a Query to update
TableA to INSERT records from TableB (ONLY RECORDS THAT DO NOT EXIST IN
TABLEA).
Thanks

 

[[MVP] S.Clark]

To find something that does not exist in another table you would use an
Outer Join.

e.g.
SELECT Customers.CustomerID
FROM Customers LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
WHERE (((Orders.CustomerID) Is Null));

So, you could use one query to find those that don't exist, then a second to
perform the Append.