How to update many rows with uniqid() making them unique in php - php

Question

I created a new column in mysql, that is going to store a unique value for all of the elements inside the database.
Now I would like to populate all rows with this unique value using uniqid().
But since the function makes use of microtime(), I can't update all rows together.
How could I do it?
$unique_id = uniqid();
$sql = "UPDATE posts SET unique_id = :unique_id";
$stmt = $pdo->prepare($sql);
$stmt->execute(['unique_id' => $unique_id]);
This code updates the same value for all rows.
How can every row be unique?

Answer 1

try with below code
SET #r := 0;
UPDATE posts
SET unique_id = (#r := #r + 1)
ORDER BY RAND();

Answer 2

Try this ,
update posts set unique_id = #i:=#i+1 order by rand();
The numbers will now randomly assigned to rows, but each row has a unique value.

Answer 3

uniqid('', TRUE),
You can use uniqid with the entropy to make it more sensitive in time to narrow down even more the chance of duplicates but keep one thing in mind:
This function does not guarantee uniqueness of return value. Since
most systems adjust system clock by NTP or like, system time is
changed constantly. Therefore, it is possible that this function does
not return unique ID for the process/thread. Use more_entropy to
increase likelihood of uniqueness.
What you can do as well is to put a random prefix like:
uniqid(mt_rand(), TRUE);
That will eliminate every chance to generate a duplicate.
You are going to use a random prefix + entropy sensitivity. The generated value will be unique even if your script runs that fast that the timestamp happens to be the same even in miliseconds.
The problem with your code is that you use uniqid() function one time by assigning it to a variable and from there you get duplicates of course cause you use this variable:
Try this code:
$sql = "UPDATE posts SET unique_id = uuid()";
$stmt = $pdo->prepare($sql);
$stmt->execute();

Answer 4

So after some tries I came across my own solution, using uniqid().
Here's my code, commented:
// Selecting all the posts
$sql = "SELECT id, pro_key FROM posts";
$stmt = $pdo->prepare($sql);
$stmt->execute();
$posts = $stmt->fetchAll();
// Looping through all the results and updating them one by one with a delay of 1 second between the updates
foreach($posts as $post) {
$sql = "UPDATE posts SET unique_id = :unique_id WHERE id = :id";
$stmt = $pdo->prepare($sql);
$stmt->execute(['id' => $post->id, 'unique_id' => uniqid()]);
// delay
sleep(1);
}
Hope this helps.