Question

I’m building a form with php/mysql. I’ve got a table with a list of locations and sublocations. Each sublocation has a parent location. A column ‘parentid’ references another locationid in the same table. I now want to load these values into a dropdown in the following manner:

--Location 1 ----Sublocation 1 ----Sublocation 2 ----Sublocation 3 --Location 2 ----Sublocation 4 ----Sublocation 5 

etc. etc.

Did anyone get an elegant solution for doing this?

Answer 1

NOTE: This is only psuedo-code.. I didn’t try running it, though you should be able to adjust the concepts to what you need.

$parentsql = 'SELECT parentid, parentname FROM table';   $result = mysql_query($parentsql);  print '<select>';  while($row = mysql_fetch_assoc($result)){     $childsql = 'SELECT childID, childName from table where parentid='.$row['parentID'];     $result2 = mysql_query($childsql);     print '<optgroup label=\'.$row['parentname'].'\'>';     while($row2 = mysql_fetch_assoc($result)){         print '<option value=\''.$row['childID'].'\'>'.$row['childName'].'</option>\n';     }     print '</optgroup>'; }  print '</select>'; 

With BaileyP’s valid criticism in mind, here’s how to do it WITHOUT the overhead of calling multiple queries in every loop:

$sql = 'SELECT childId, childName, parentId, parentName FROM child LEFT JOIN parent ON child.parentId = parent.parentId ORDER BY parentID, childName';   $result = mysql_query($sql); $currentParent = '';  print '<select>'; while($row = mysql_fetch_assoc($result)){     if($currentParent != $row['parentID']){         if($currentParent != ''){             print '</optgroup>';         }         print '<optgroup label=\'.$row['parentName'].'\'>';         $currentParent = $row['parentName'];     }      print '<option value=\''.$row['childID'].'\'>'.$row['childName'].'</option>\n'; } print '</optgroup>' print '</select>';