Is this possible? Update a dataset with info in another dataset

Question

I have dataset 1 from an SQL table which has 'x' number of columns, the two I'm interested in happened to be named 'mcmcu' and 'mcdl01' I have dataset 2 from a different SQL table with only 2 columns, named 'costcenter' and 'description' I want to insert into dataset 2 any 'mcmcu' records from dataset1 which don't exist in dataset 2. I want to update the description in dataset 2 any 'mcmcu' records from dataset1 that do exist. Then I want to update dataset 2 back to SQL. I've been farting around with this but haven't been able to get it to work. Is this possible? Any insight on how would be greatly appreciated. Thanks in advance, J Greene