Fetch SQL data from same table of different column - php

Question

I'm using get request to fetch serial and put it into query.
$id = $_GET['id'];
$select = $pdo->prepare("SELECT * FROM tbl_product WHERE serial='.$id.'");
$select->execute();
while($row = $select->fetch(PDO::FETCH_OBJ)){
echo '
<tr>
<td>'.$row->pname.'</td>
<td>'.$row->pcategory.'</td>
<td>'.$row->serial.'</td>
<td>'.$row->sku.'</td>
';
}
My table look like this, I tried using inner join for same table but it didn't work.
When user key in serial through get request localhost?id=12345678 . I want it to show item1 - item3, that match with its SKU
id | sku | serial | product_name
0 | ABC | 12345678 | item1
1 | ABC | 87654321 | item2
2 | ABC | 23456789 | item3
3 | DEF | 56789234 | item4

Answer 1

Something like
select * from tbl_product where sku = (select sku from tbl_product where serial = :serial)
might do it, presuming a PDO prepared statement.

Answer 2

You can try inner join like this:
select id, c.sku, serial, product_name from table_name t
inner join (
select sku from table_name where serial ='12345678'
)c on t.sku = c.sku
in your code:
$id = $_GET['id'];
$query = "select id, c.sku, serial, product_name from table_name t
inner join (
select sku from table_name where serial = :serial
)c on t.sku = c.sku";
$select = $pdo->prepare($query);
$select->bindParam(':serial', $id);
$select->execute();
while($row = $select->fetch(PDO::FETCH_OBJ)){
echo '
<tr>
<td>'.$row->pname.'</td>
<td>'.$row->pcategory.'</td>
<td>'.$row->serial.'</td>
<td>'.$row->sku.'</td>
';
}
Don't trust any input, use prepare, and bindParam to avoid SQL injection. You can reference SQL injection here https://www.php.net/manual/en/security.database.sql-injection.php

Answer 3

Self join
$select = $pdo->prepare("SELECT * FROM tbl_product P1 LEFT JOIN tbl_product P2 ON P2.sku = P1.sku WHERE P1.serial='.$id.'")