Php Calender Week Random User Calculation - php

Question

I got an database (phpmyadmin) in which I put users,
grid looks like this
+-----+---------+-----------------+----------------+
| id | user | categorie_bit | calender_week |
+-----+---------+-----------------+----------------+
| 1 | Kevin | 01 | 39 |
+-----+---------+-----------------+----------------+
the id and user is self explained. Categorie_bit stands for the current job he / she has to do like having a walk with the dog.
0 - no job
1 - job 1
10 - job 2
11 - both jobs
and the calender week shows the current calender week.
like this in php:
$date = new DateTime();
echo $date->format('W');
I got various users, each user has to do a job for this calenderweek for this instance 39.
The user is picked randomly from the database. (I used a PDO Wrapper)
$table = "users";
$columns = array("id", "firstname");
$orderBy = array('RAND()');
$result_set = $db->select($table,$columns, Null, Null, $orderBy, 1);
In the next step I give the user a "job".
Categorie_bit = 1.
The problem is now that I want to pick a user who did not have a "job" last calender week, so that all users are treated equally.
Edit:
How do I accomplish this for further usage, lets say user 1 had to work week 39 and user 2 for week 44 and so on...
My first idea is to change the random picker somehow.
Anyone knows how to accomplish this?

Answer 1

Just add a WHERE clause to your query checking if there's an entry last week for your user. I'm not familiar with your PDO wrapper but the resultant query should be:
SELECT u.id, u.firstname
FROM users u
WHERE (
SELECT COUNT(*)
FROM users u2
WHERE u.id = u2.id
AND u2.calendar_week = <?= $date->format('W') - 1 ?>
AND u2.categorie_bit > 0
) = 0
ORDER BY RAND()
LIMIT 1
UPDATE
To make sure each user wasn't assigned another job until every user had done a job at least once I would record the information differently. I would have two tables, one for users and one for the job they completed and the week they completed it on.
Users
+----+-------+
| id | user |
+----+-------+
| 1 | Kevin |
+----+-------+
Jobs
+----+--------+-----+------+
| id | userId | job | week |
+----+--------+-----+------+
| 1 | 1 | 01 | 39 |
| 2 | 2 | 10 | 39 |
| 3 | 6 | 01 | 40 |
| 4 | 8 | 10 | 40 |
+----+--------+-----+------+
Then you can use the following query:
SELECT u.id, u.user
FROM users u
LEFT JOIN jobs j ON u.id = j.userId
WHERE j.id IS NULL
ORDER BY RAND()
LIMIT 1
So now you only get users who haven't completed a job. Once everyone has completed a job and the query returns 0 results you just clear the jobs table and start afresh.