Sql request to get an ordered menu - mysql

Question

Right now, I build my menu doing many request and loop with symfony.
I would like to be able to retrieve the same thing in a single sql request
MenuItem (Id,parent_id,level,weight)
parent_id is a reference to an other MenuItem
If I have these records
1,null,1,50
2,null,1,20
3,1,2,100
4,1,2,0
5,2,2,40
6,5,3,900
7,5,3,500
I want the results to be
2
5
7
6
1
4
3
The weigtht attribute is used to order the menu items inside their own level.
That means id 2 come before id 1 because weight 20 < weight 50 but id 2 still comes before id 4 because level 1 < level 2
I'm not even sure this is possible.
EDIT: Right now, I have to do something very ugly
$menu = $this->factory->createItem('root');
$menu->setLabel("Menu");
$item_repository = $this->getDoctrine()->getRepository(MenuItem::class);
//profondeur max defini à 5
//On récupère les items du niveau 1 trié par poids (profondeur)
$items_lv1 = $item_repository->findBy(array('menu' => $id_main_menu,'active' => 1, 'niveau' => 1),array('poids' => 'ASC'));
//On récupère les items du niveau 2 trié par parent et poids (profondeur)
$items_lv2 = $item_repository->findBy(array('menu' => $id_main_menu,'active' => 1,'niveau' => 2),array('parent' => 'ASC','poids' => 'ASC'));
$items_lv3 = $item_repository->findBy(array('menu' => $id_main_menu,'active' => 1,'niveau' => 3),array('parent' => 'ASC','poids' => 'ASC'));
$items_lv4 = $item_repository->findBy(array('menu' => $id_main_menu,'active' => 1,'niveau' => 4),array('parent' => 'ASC','poids' => 'ASC'));
$items_lv5 = $item_repository->findBy(array('menu' => $id_main_menu,'active' => 1,'niveau' => 5),array('parent' => 'ASC','poids' => 'ASC'));
$cptLv1 = 1;
foreach ($items_lv1 as $item_lv1){
$lv1 = $menu->addChild($cptLv1,
['uri' => $item_lv1->getUrl(),'label' => $item_lv1->getLabel(),
'attributes' => array('title' => $item_lv1->getTitle(),
'id_css' => $item_lv1->getIdCss(), 'class_css' => $item_lv1->getClassCss(), 'target' => $item_lv1->getTarget())]);
$cptLv2 = 1;
foreach ($items_lv2 as $item_lv2){
if($item_lv2->getParent()->getUrl() == $item_lv1->getUrl()){
$lv2 = $lv1->addChild($cptLv1.$cptLv2,
['uri' => $item_lv2->getUrl(),'label' => $item_lv2->getLabel(),
'attributes' => array('title' => $item_lv2->getTitle(),
'id_css' => $item_lv2->getIdCss(), 'class_css' => $item_lv2->getClassCss(), 'target' => $item_lv2->getTarget())]);
$cptLv3 = 1;
foreach ($items_lv3 as $item_lv3){
if($item_lv3->getParent()->getUrl() == $item_lv2->getUrl()) {
$lv3 = $lv2->addChild($cptLv1.$cptLv2.$cptLv3,
['uri' => $item_lv3->getUrl(), 'label' => $item_lv3->getLabel(),
'attributes' => array('title' => $item_lv3->getTitle(),
'id_css' => $item_lv3->getIdCss(), 'class_css' => $item_lv3->getClassCss(), 'target' => $item_lv3->getTarget())]);
$cptLv4 = 1;
foreach ($items_lv4 as $item_lv4){
if($item_lv4->getParent()->getUrl() == $item_lv3->getUrl()) {
$lv4 = $lv3->addChild($cptLv1.$cptLv2.$cptLv3.$cptLv4,
['uri' => $item_lv4->getUrl(), 'label' => $item_lv4->getLabel(),
'attributes' => array('title' => $item_lv4->getTitle(),
'id_css' => $item_lv4->getIdCss(), 'class_css' => $item_lv4->getClassCss(), 'target' => $item_lv4->getTarget())]);
$cptLv5 = 1;
foreach ($items_lv5 as $item_lv5){
if($item_lv5->getParent()->getUrl() == $item_lv4->getUrl()) {
$lv4->addChild($cptLv1.$cptLv2.$cptLv3.$cptLv4.$cptLv5,
['uri' => $item_lv5->getUrl(), 'label' => $item_lv5->getLabel(),
'attributes' => array('title' => $item_lv5->getTitle(),
'id_css' => $item_lv5->getIdCss(), 'class_css' => $item_lv5->getClassCss(), 'target' => $item_lv5->getTarget())]);
}
$cptLv4 += 1;
}
}
$cptLv4 += 1;
}
}
$cptLv3 += 1;
}
}
$cptLv2 +=1;
}
$cptLv1+=1;
}

Answer 1

Consider the following:
DROP TABLE IF EXISTS my_table;
CREATE TABLE my_table
(id SERIAL PRIMARY KEY
,parent_id INT NULL
,level INT NOT NULL
,weight INT NOT NULL
);
INSERT INTO my_table VALUES
(1,null,1,50),
(2,null,1,20),
(3,1,2,100),
(4,1,2,0);
SELECT *,COALESCE(y.level,x.level) my_level,COALESCE(y.weight,x.weight) my_weight FROM my_table x LEFT JOIN my_table y ON y.id = x.parent_id;
+----+-----------+-------+--------+------+-----------+-------+--------+----------+-----------+
| id | parent_id | level | weight | id | parent_id | level | weight | my_level | my_weight |
+----+-----------+-------+--------+------+-----------+-------+--------+----------+-----------+
| 1 | NULL | 1 | 50 | NULL | NULL | NULL | NULL | 1 | 50 |
| 2 | NULL | 1 | 20 | NULL | NULL | NULL | NULL | 1 | 20 |
| 3 | 1 | 2 | 100 | 1 | NULL | 1 | 50 | 1 | 50 |
| 4 | 1 | 2 | 0 | 1 | NULL | 1 | 50 | 1 | 50 |
+----+-----------+-------+--------+------+-----------+-------+--------+----------+-----------+
Extract from that whatever you like.

Answer 2

you do not have to use level and weight ... just use the weight ("order" would be better).
do not worry if id 2 is before or after id 4, because id4 is in id2 (parent level).
an element with parent_id = null is a id with level 0.
think like this :
select Id,parent_id,level ,weight from mytable order by level,weight
Here is a piece of code that allows you, after your select, to have a recursive table that you can browse to display the menus.
It takes into account that an element can be related to "null" (root), and that there can be non-consecutive "weights" ...
the $ result variable is constructed as if you had made a select with a sort on level + weight
<style>
ul {
list-style-type: none;
margin: 0;
padding: 0;
background-color: #D0D0D0;
}
li {
margin-left:2em;
border-left:solid 2px green;
text-align:left;
padding-left:1em;
}
</style>
<?php
/*
* warn ! this array looks like a result after a select, ordered by level+weight
*/
$result=array(
array( 'id'=>2, 'parent_id'=>null, 'level'=>1, 'weight'=>20 ),
array( 'id'=>1, 'parent_id'=>null, 'level'=>1, 'weight'=>50 ),
array( 'id'=>4, 'parent_id'=>1, 'level'=>2, 'weight'=>0 ),
array( 'id'=>3, 'parent_id'=>1, 'level'=>2, 'weight'=>100 ),
array( 'id'=>5, 'parent_id'=>2, 'level'=>2, 'weight'=>40 ),
array( 'id'=>7, 'parent_id'=>5, 'level'=>3, 'weight'=>500 ),
array( 'id'=>6, 'parent_id'=>5, 'level'=>3, 'weight'=>900 )
);
// store recursive array of menus
$menus=array();
// store link of an id in the recursive array of menus
$keysIds=array();
// start with a empty menu
$menus[0]=array('element'=>'ROOT','subMenus'=>array());
$keysIds[0]=&$menus[0];
// build a menus array
foreach ($result as $element) {
$idParent=$element['parent_id'];
$id=$element['id'];
// check for idParent=0 !!
if ($idParent==null) {
$idParent=0;
}
// check if parent exists
// don't forget, result is sorted by level+weight,
// so the idParent is always in array
if (!isset($keysIds[$idParent])) {
echo "<H2>PARENT = $idParent , not exists while INSERTING Id {$id} </H2>";
continue;
}
// JSON index sorting prevention
$max=sizeof($keysIds[$idParent]['subMenus']);
// create a entry
$keysIds[$idParent]['subMenus'][$max]=array('element'=>$element,'subMenus'=>array());
// for next entries, keep this id accessible quickly..it can be a parent.
$keysIds[$id]=&$keysIds[$idParent]['subMenus'][$max];
}
// show the HTML LISTE
htmlMenus($menus,0);
// Recursive iteration on $menus
function htmlMenus($root,$listeLevel) {
echo str_repeat(" ", $listeLevel*2); // beautifull source...
echo "<ul>\n";
foreach ($root as $datas) {
echo str_repeat(" ", $listeLevel*2+2);
echo "<li>\n ";
if ($datas['element']!='ROOT') {
echo str_repeat(" ", $listeLevel*2+2);
echo "ID : {$datas['element']['id']} weight:{$datas['element']['weight']}\n";
}
htmlMenus($datas['subMenus'],$listeLevel+1);
echo str_repeat(" ", $listeLevel*2+2);
echo '</li>';
}
echo str_repeat(" ", $listeLevel*2);
echo "</ul>\n";
}