Update target where source ""

Question

Access 2013. I have two tables with the same structure, ML and MLTemp. I want to update ML from MLTemp whith the fields in MLTemp which are not empty, that is I want to avoid writing an empty value from MLTemp into a field in ML that has a value already.
Is there a way to do that in VBA/SQL without looping through each field in MLTemp and check if it's not empty?
Best regards George

Answer 1

Assuming that there is a primary key/unique index field on which you can join the tables:
UPDATE ML INNER JOIN MLTemp ON ML.ID = MLTemp.ID SET ML.Field1 = Nz([ML].[Field1],[MLTemp].[Field1]), ML.Field2 = Nz([ML].[Field2],[MLTemp].[Field2]), ML.Field3 = Nz([ML].[Field3],[MLTemp].[Field3]);
Here, ID is the primary key, and Field1, Field2 and Field3 are the fields to be updated.
If MLTemp also contains records that don't have a matching ID in ML, you can add them using:
INSERT INTO ML
SELECT MLTemp.*
FROM MLTemp LEFT JOIN ML ON MLTemp.ID = ML.ID
WHERE ML.ID Is Null;
Regards, Hans Vogelaar (http://www.eileenslounge.com)