create a sequence for rows with similar ids using php - php

Question

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 1

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();
?>

Answer 2

Your update query
$query2 = "update foo set value = :multiple";
does not contain any where criteria, each time you call this query it updates the value field's value in all records.
Honestly, I would not really involve php in this update, would do it purely in sql using user defined variables and multi-table join syntax in the update:
update foo inner join (select #i:=0, #previd:=-1) as a
set foo.value=concat(foo.value,'_',#i:=if(id=#previd,#i+1,0),if(#previd:=id,'',''))
The subquery in the inner join initialises #i and #previd user defined variables. The 3rd parameter of the concat function determines the value #i to be concatenated to the value field. The 4th parameter of concat sets the #previd variable and returns an empty string not to affect the overall concatenation. Unfortunately, I do not have access to MySQL to test the query, but it should be a good starting point anyway.
UPDATE
The OP claims in the updated question that the query I provided creates the below resultset:
+------+-----------------------------------------------+
| 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 |
+------+-----------------------------------------------+
Tested my solution in sqlfiddle. I had to remove the order by clause, otherwise the query produced the results in line with the requirements stated in the question. See sqlfiddle for details.
The results in the updated question are likely the result of running the query in a loop multiple times. In simple words: you just copy pasted the query into your code and did not remove the loop, even when I pointed out, that this may be the reason of the results you received.