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

Is your problem "However, in theory someone could update the cost column on the materials table between the two queries, in which case the calculated percents will be off."?

In that case , probably you can simply use a inner query as:

SELECT material_id, cost/(SELECT Sum(cost)
  FROM materials
  WHERE material_id >=0
  AND material_id <= 10)
INTO v_material_id_collection, v_pct_collection
FROM materials
WHERE material_id >=0
AND material_id <= 10;

Why do you want to lock a table? Other applications might fail if they try to update that table during that time right?