Why can't I use SELECT … FOR UPDATE with aggregate functions?

Question

I have an application where I find a sum() of a database column for a set of records and later use that sum in a separate query, similar to the following (made up tables, bu

Answer 1

You might try something like:

<>
declare
  material_id materials.material_id%Type;
  cost        materials.cost%Type;
  total_cost  materials.cost%Type;
begin
  select material_id,
         cost,
         sum(cost) over () total_cost
  into   local.material_id,
         local.cost,
         local.total_cost 
  from   materials
  where  material_id between 1 and 3
  for update of cost;

  ...

end local;

The first row gives you the total cost, but it selects all the rows and in theory they could be locked.

I don't know if this is allowed, mind you -- be interesting to hear whether it is.