Question

I have some code like this:

Update table_name
set
[column] = case when d.data is null, then null else d.columnname end.

from...
etc

My question is, how do I set up a function where the ‘else d.columnname’ is to sum up several columns from joins.

Would it be something like:

 ...then null else sum(d.column1 + rf.column2 + rwf.column3) as tempcolumn end,

or

...then null else (d.column1 + rf.column2 + rwf.column3) end,

What is the correct way to do a column sum in this set situation?

Answer 1

You can simply do:

update MyTable
set column =
    case 
        when d.data is not null 
        then d.column1 + rf.column2 + rwf.column3 
    end
from ...

CASE will return NULL by default when there is no match.