tom sawyer tom sawyer - 4 months ago 13
MySQL Question

create a sequence for rows with similar ids using php

i have a datastructure similar to this



+---------+---------+
| id | value |
+---------+---------+
| 1 | value |
1 | value |
| 1 | value |
| 1 | value |
| 1 | value |
| 2 | value |
| 2 | value |
| 2 | value |
| 3 | value |
| 3 | value |
| 3 | value |
| | |
+---------+---------+





I am trying to update this table to look something like this



+---------+---------+
| id | value |
+---------+---------+
| 1 | value 0 |
1 | value 1 |
| 1 | value 2 |
| 1 | value 3 |
| 1 | value 4 |
| 2 | value 0 |
| 2 | value 1 |
| 2 | value 2 |
| 3 | value 0 |
| 3 | value 1 |
| 3 | value 2 |
| | |
+---------+---------+





To achieve this, i have written php script that looks like this



$query = "select count(*) as count,id, value from foo group by id";
$sql=$con->prepare($query);
$sql->execute();
$sql->setFetchMode(PDO::FETCH_ASSOC);

while($row=$sql->fetch()){
$id[] = $row['id'];
$count[] = $row['count'];
$value[] = $row['value'];
echo "<pre>";
}
$c=array_combine($id, $count);
foreach ($c as $key=>$value){

for($i=0;$i<=$value;$i++){
$postid = $key;
if($i==0){
$multiple = "multiple";
$newvalue= $value;
}
else{
$x=$i-1;
$multiple = "multiple_".$x;
echo $multiple . "<br>";
$query2 = "update foo set value = :multiple";
$sql2=$con->prepare($query2);
$sql2->bindValue(':multiple', $multiple);
$sql2->execute();

}
}
}





The problem is that the code returns the following results



+---------+---------+
| id | value |
+---------+---------+
| 1 | value_1 |
1 | value_1 |
| 1 | value_1 |
| 1 | value_1 |
| 1 | value_1 |
| 2 | value_1 |
| 2 | value_1 |
| 2 | value_1 |
| 3 | value_1 |
| 3 | value_1 |
| 3 | value_1 |
| | |
+---------+---------+




What can i be possibly be doing wrong?

Thanks @Shadow

Your query runs fine but returns the following results



+------+-----------------------------------------------+
| id | value |
+------+-----------------------------------------------+
| 1 | multiple_1_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0 |
| 1 | multiple_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1 |
| 1 | multiple_1_2_2_2_2_2_2_2_2_2_2_2_2_2_2_2_2 |
| 1 | multiple_1_3_3_3_3_3_3_3_3_3_3_3_3_3_3_3_3 |
| 2 | multiple_1_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0 |
| 2 | multiple_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1 |
| 2 | multiple_1_2_2_2_2_2_2_2_2_2_2_2_2_2_2_2_2 |
| 2 | multiple_1_3_3_3_3_3_3_3_3_3_3_3_3_3_3_3_3 |
| 3 | multiple_1_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0 |
| 3 | multiple_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1_1 |
| 3 | multiple_1_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0_0 |
+------+-----------------------------------------------+




Answer

You can do the update iterating and creating data in such a way:

<?php
$pdo = new PDO('mysql:host=localhost;dbname=test', 'root', '');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sth = $pdo->prepare("SELECT * FROM foo");
$sth->execute();
$data = $sth->fetchAll(PDO::FETCH_ASSOC);

$response = array();
foreach ($data as $dataIndex => $dataValue) {

    if (!isset($response[$dataValue["id"]]["count"])) {
        $response[$dataValue["id"]]["count"] = 0;
    } else {
        $response[$dataValue["id"]]["count"] ++;
    }

    $response[$dataValue["id"]]["values"][$dataValue["pid"]] = "value_" . $response[$dataValue["id"]]["count"];

    $sth = $pdo->prepare("UPDATE foo SET value = '{$response[$dataValue["id"]]["values"][$dataValue["pid"]]}' WHERE pid = {$dataValue["pid"]}");
    $sth->execute();
}
?>

But try to do an update using the least iteration not to create as many database queries , example:

<?php
$pdo = new PDO('mysql:host=localhost;dbname=test', 'root', '');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sth = $pdo->prepare("SELECT * FROM foo");
$sth->execute();
$data = $sth->fetchAll(PDO::FETCH_ASSOC);

$response = array();
$update = array();
foreach ($data as $dataIndex => $dataValue) {
    $response[$dataValue["id"]]["id"] = $dataValue["id"];

    if (!isset($response[$dataValue["id"]]["count"])) {
        $response[$dataValue["id"]]["count"] = 0;
    } else {
        $response[$dataValue["id"]]["count"] ++;
    }

    $response[$dataValue["id"]]["values"][$dataValue["pid"]] = "value_" . $response[$dataValue["id"]]["count"];
    $update[] = "UPDATE foo SET value = '{$response[$dataValue["id"]]["values"][$dataValue["pid"]]}' WHERE pid = {$dataValue["pid"]};";
}
$update = implode("",$update);
$sth = $pdo->prepare($update);
$sth->execute();
?>