Update question

Hi all:

I have a table like this:

Table cost

Id  edge_id    cost

1       30         101.4

2       30          null

3       40          500.2

4       40           null

5        45          300.7

6        45           null

I want to set cost value with same edge_id by same value. The existing values are calculated by calling a function (calculate edge length). I can calculate the value by same function, but the function was slow. I wander if I can use update statement to set the second value with same edge_id. Thanks in advance for your help.

Fay