Multiple Select Dropdown and Array

I was working on this a couple of months back and could not figure out
what I was doing wrong. I came back to it today and wanted to post
again to see if any of you had an idea. Here is the problem.

I have this code:

<select name="myrep[RepFor][]" size="3" multiple="multiple">
  <%= options_from_collection_for_select(@rflists, "id", "keyword",
@selected) %>
</select>

The field I am storing is called RepFor in the myrep table. The
options for the dropdown comes from a keyword table that have an id
and name. The options I want have been fed into rflists. This all
works good and displays properly with a multiple select dropdown with
the proper names and values. Here is the html it renders:

<select name="myrep[RepFor][]" size="3" multiple="multiple">
  <option value="1808">Car Insurance</option>
<option value="1809">Home Insurance</option>
<option value="1810">Technology</option>
<option value="1811">Accounting</option>
<option value="1812">Legal</option>

So if I select Car Insurance, Home Insurance and Technology and submit
it this is what gets written to the DB. Exactly as shown below.

--- - "1808" - "1809" - "1810"

When I reopen the form nothing is selected.

Now if I manually set @selected in my code as follows it selects the
items I have forced when I reopen the form:

<% @selected = 1808, 1809, 1810 %>
<select name="myrep[RepFor][]" size="3" multiple="multiple">
  <%= options_from_collection_for_select(@rflists, "id", "keyword",
@selected) %>
</select>

My question is what do I need to do to make the select write the data
to the DB the same way I set it in @selected. Is there something that
has to be done in the controller to keep it from being written as
follows:

--- - "1808" - "1809" - "1810"

or do I need to do something special when reading it back?

Thanks for your help.

Jim

That is a Var Char in a mysql DB. All the selections sit in one
field, the RepFor field in the table. The code:

<select name="myrep[RepFor][]" size="3" multiple="multiple">
  <%= options_from_collection_for_select(@rflists, "id", "keyword",
@selected) %>
</select>

writes that to the RepFor field in the myrep table. There is no
special code in controller. I guess thats my question. What needs to
be in there to write the values seperated by commas so that when I
pull the field back in edit mode the entries are selected on the
form. Alternately what do I need to do to get the multi select as I
have it to work. Its crazy to me that this is not so
straightforward. I must be missing some easy step. Do I need to do
some sort of translation on the controller side? Do I need to store
it in the DB in some other way?