Mysql one Parent multiple Child result without repeating Parent rows - php

Question

I am building a CMS with Codeigniter and MYSQL. and have a table like this.
CREATE TABLE parent
(`parentId` int, `parentName` varchar(50));
INSERT INTO parent
(`parentId`, `parentName`)
VALUES
(1, 'Movie'),
(2, 'Food'),
(3, 'Sports');
CREATE TABLE child
(`childId` int, `parentId` int,`childName` varchar(50));
INSERT INTO child
(`childId`, `parentId`, `childName`)
VALUES
(1, 1, 'Harry Potter'),
(2, 3, 'Foot Ball'),
(3, 2, 'Pizza'),
(4, 2, 'Burger'),
(5, 1, 'Avengers'),
(6, 1, 'Fury'),
(7, 3, 'Cycling');
And want output to be printed output like this
foreach($parent as $parentData):
echo"<h4>".$parentData->parentName."</h4>";
echo"<ul>";
foreach($child as childData):
echo"<li>".$childData->childName."</li>";
endforeach;
echo"</ul>"
endforeach;
which produces this
<h4>Movie</h4>
<ul>
<li>Harry Potter</li>
<li>Avengers</li>
<li>Fury</li>
</ul>
<h4>Food</h4>
<ul>
<li>Pizza</li>
<li>Burger</li>
</ul>
<h4>Sports</h4>
<ul>
<li>Foot Ball</li>
<li>Cycling</li>
</ul>
Any tweaking of the code is welcomed.
As i have been trying this for the past few hours.
Thanks in advance.
Update:
I implemented the answer to my code as CodeGodie suggested and added a view like this.
foreach ($result as $arr) {
if (!isset($final[$arr["parentName"]])) {
$final[$arr["parentName"]] = array();
}
array_push($final[$arr["parentName"]], $arr);
}
foreach ($final as $parent=> $childs) {
echo $parent."<br>";
foreach ($childs as $child) {
print_r($child) ;
}
}
Now i got the result i was expecting

Answer 1

There are multiple ways of doing this. However I would use the following approach:
You need to create the following SQL query:
SELECT * FROM parent p
JOIN child c ON c.parentId = p.parentId
ORDER BY parentName
Or in Codeigniter:
$this->db->select("*");
$this->db->from("parent p");
$this->db->join("child c", "c.parentId = p.parentId ");
$this->db->order_by("parentName");
$q = $this->db->get();
return $q->result_array();
which will give you a result of something like this:
$result = array(
array(
"parentId" => 2,
"parentName" => "Food",
"childId" => 3,
"childName" => "Pizza",
),
array(
"parentId" => 2,
"parentName" => "Food",
"childId" => 4,
"childName" => "Burger",
),
array(
"parentId" => 1,
"parentName" => "Movie",
"childId" => 1,
"childName" => "Harry Potter",
),
array(
"parentId" => 1,
"parentName" => "Movie",
"childId" => 5,
"childName" => "Avengers",
)
);
Iterate through your results:
foreach ($result as $arr) {
if (!isset($final[$arr["parentName"]])) {
$final[$arr["parentName"]] = array();
}
array_push($final[$arr["parentName"]], $arr);
}
var_dump($final);
this will give you a result like this which you can then iterate to build your HTML:
array (size=2)
'Food' =>
array (size=2)
0 =>
array (size=4)
'parentId' => int 2
'parentName' => string 'Food' (length=4)
'childId' => int 3
'childName' => string 'Pizza' (length=5)
1 =>
array (size=4)
'parentId' => int 2
'parentName' => string 'Food' (length=4)
'childId' => int 4
'childName' => string 'Burger' (length=6)
'Movie' =>
array (size=2)
0 =>
array (size=4)
'parentId' => int 1
'parentName' => string 'Movie' (length=5)
'childId' => int 1
'childName' => string 'Harry Potter' (length=12)
1 =>
array (size=4)
'parentId' => int 1
'parentName' => string 'Movie' (length=5)
'childId' => int 5
'childName' => string 'Avengers' (length=8)
Hope this helps

Answer 2

I think you are looking for group concat
https://www.percona.com/blog/2013/10/22/the-power-of-mysqls-group_concat/
Using this, you can select a comma separated list of child values. Then in your PHP you would simply need to explode on the comma and then loop through that.
Bear in mind the default group_concat limit is often quite low so you will probably need to increase this - https://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html#sysvar_group_concat_max_len

Answer 3

This query will get all the data:
SELECT parent.parentName, child.childName
FROM parent
INNER JOIN child on parent.parentId = child.parentId;
And return it as:
------------------------------
parentname | childName
------------------------------
Movie | Harry Potter
Movie | Avengers
Movie | Fury
et cetera...