Try this:
>From your code:
<tr>
<td><b>Part Name:</b></td>
<td><input type="text" name="partname" size=20></td>
</tr>
change to:
<td><b>Part Name:</b></td>
<td>
<select name="partname">
<option value="">Select partname </option>
<dtml-in listPartName_sql>
<option><dtml-var partname></option>
</dtml-in>
</select>
</td>
ZSQL method: listPartName
===================
select * from PartNameTable