Thank you for this post. The last block of code wont run for me in snowflake . I changed ON to WHERE.

UPDATE ToTable as t2
    set val = r.total
    from (
        select ID, 
            sum(HiddenCash) + sum(Cash) + sum(income) as total
        from  SourceTable
        group by ID
    ) as r 
        on t2.ID= r.ID;


UPDATE ToTable as t2
    set val = r.total
    from (
        select ID, 
            sum(HiddenCash) + sum(Cash) + sum(income) as total
        from  SourceTable
        group by ID
    ) as r 
        where t2.ID= r.ID;