UPDATE - CASE Statement - Way too many results

Question

I'm trying to do a very simple data insert on a table using a case statement, see below:

begin tran
  update tblworkitems
  set fkidsupplier = (
    case
    when idworkitem = 214159 then 50290
    when idworkitem = 270370 then 50367
    when idworkitem = 225533 then 50453
    ...
    end )
where 
fkidtemplateitem = 654 and
fkidsupplier is null

I have ~85 of these explicit values. idWorkItem is a primary key, fkidSupplier is a foreign key (Hungarian notation much?). Problem is ~350 row are being returned. I've done this with similar things a million times before and have never had this.

A quick check confirms no duplicates (schema should enforce this anyway):

select idworkitem 
from tblworkitems 
where fkidtemplateitem = 654
group by idworkitem having count(*) > 1

Yes, I understand the WHERE clause is invalid with these primary keys.

Any ideas?

Answer 1

With the structure you have, you still update all the records that meet the criteria in WHERE clause. For those that are not specified in CASE , it will simply set NULL .

What you should do is to specify all records with idworkitem that you want to update in WHERE clause.