SQL update from one Table to another based on a ID match

Question

I have a database with account numbers and card numbers. I match these to a file to update any card numbers to the account number, so

Answer 1

The below SQL someone suggested, does NOT work in SQL Server. This syntax reminds me of my old school class:

UPDATE table2 
SET table2.col1 = table1.col1, 
table2.col2 = table1.col2,
...
FROM table1, table2 
WHERE table1.memberid = table2.memberid

All other queries using NOT IN or NOT EXISTS are not recommended. NULLs show up because OP compares entire dataset with smaller subset, then of course there will be matching problem. This must be fixed by writing proper SQL with correct JOIN instead of dodging problem by using NOT IN. You might run into other problems by using NOT IN or NOT EXISTS in this case.

My vote for the top one, which is conventional way of updating a table based on another table by joining in SQL Server. Like I said, you cannot use two tables in same UPDATE statement in SQL Server unless you join them first.