>So, turn the UPDATE into select into CTE first and then UPDATE CTE if there is always 1 to 1 relation between table to update and the other tables.
If this would be a single update, that would do. I would be able to select into a temporary table and use that table in the second command (the update). But, in this case, this is a massive update of all the records in the table so I do not think this approach could work.