I have a drop-down select menu that contains 10 departments (Department table) in my company. Each department is linkedo one of 5 branches (Branch table). When a user fills out a form and choses a department I want it to autopopulate a text input box with the appropriate branch.
This is the query I want run each time a department is chosen:
Select BranchName from Department where Department= The select box value.

Here is what I have so far. Please help with the JS function:
<SELECT NAME="Directorate" onChange="GetBranch()">
    <OPTION VALUE="Accounting">Accounting
    <OPTION VALUE="MIS">MIS
        <OPTION VALUE="Marketing">Marketing
etc....
</SELECT>
<input type="text" name="branch> <--This field is dynamically populated by the GetBranch() JS function

You could load the data into clientside Javascript arrays or just if / case statements to populate the code, faster to execute, but adds to the download.

Otherwise, you'll have to submit the entire page to the server and get it to reprocess it.

Personally I'd hide an iFrame or Frame in there and use that to communicate with the server and then use Javascript in the response from the server side component to populate the main form, giving you the best of both worlds.

If you are not going to make any database operations based on page and if the page is for just view only then make the code from

<SELECT NAME="Directorate" onChange="GetBranch()">
<OPTION VALUE="Accounting">Accounting
<OPTION VALUE="MIS">MIS
<OPTION VALUE="Marketing">Marketing
</SELECT>

to

<SELECT NAME="Directorate" onChange="GetBranch()">
<OPTION VALUE="Branch1">Accounting
<OPTION VALUE="Branch2">MIS
<OPTION VALUE="Branch3">Marketing
</SELECT>
GetBranch(){
document.forms[0].branch.value=document.forms[0].Directorate[document.forms[0].Directorate.selectedIndex].value
}

or u need to submit the form and u need to reprocess it

In the SELECT it can be that the value does not agree with the visible text:

<select name="Directorate" onChange="getBranch()">
   <option value="accounting">Accounting</option>
   <option value="mys">Mys preferences</option>
   <option value="marketing">The new marketting</option>
</select>
<input type="text" name="branch>

Then the function would change a little:

getBranch(){
document.forms[0].branch.value=document.forms[0].Directorate[document.forms[0].Directorate.selectedIndex].text
}