Random uniqueID for each ID SQL

Question

How can I improve this code? I wanted to know if there's a possibility to remove the for loop, and UPDATE a different uniqueID for each ID in my database.

<?php

  $reponse = $bdd->prepare("SELECT MAX(ID) FROM tuto WHERE title=''");
  $reponse->execute();

  $IDnow = $reponse->fetch(PDO::FETCH_ASSOC);
  $IDnow = $IDnow['MAX(ID)'];

  for ($i=2 ; $i <= $IDnow ; $i++){

     $reponse = $bdd->prepare("UPDATE tuto SET uniqueID=:uniqueID WHERE uniqueID='' AND title='' AND ID=:i");

     $uniqueID = $donnees['uniqueID'];

     $int = rand(0,51);
     $a_z = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
     $uniqueID = time().$a_z[$int];

     $reponse->execute([':uniqueID' => $uniqueID, 'i' => $i]);
  }
?>

Answer 1

Finally, I used RAND(), for generate an "UniqueID", and we can add some letters after or else :

Thanks to NerdyDev and Bart Friederichs for solutions.

<?php

$reponse = $bdd->prepare("UPDATE tuto SET uniqueID=ROUND(RAND() * :tp) WHERE uniqueID='' AND title=''");

$uniqueID = $donnees['uniqueID'];

$tp = time();
$reponse->execute([':tp' => $tp]);

?>

Answer 2

using foreach() loop will resolve your question.

<?php
$reponse = $bdd->prepare("SELECT MAX(ID) FROM tuto WHERE title=''");
$reponse->execute();
$IDnow = $reponse->fetch(PDO::FETCH_ASSOC);
$IDnow1 = $IDnow['MAX(ID)'];

foreach ($IDnow1 as $IDnow){
    $reponse = $bdd->prepare("UPDATE tuto SET uniqueID=:uniqueID WHERE uniqueID='' AND title='' AND ID=:i");
    $uniqueID = $donnees['uniqueID'];
    $int = rand(0,51);
    $a_z = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $uniqueID = time().$a_z[$int];
    $reponse->execute([':uniqueID' => $uniqueID, 'i' => $IDnow]);
  }
?>

let me know if still any issue stands with your question. Good Luck!