Question

i’ve 2 tables. In table_1 i’ve got different tasks that is updated every day. And in table_2 i’ve got list of workers. I need automatically and randomly assign 1 worker(table_2) to 1 task(table_1), so that every worker will have approximately the same amount of tasks.

I’ve tried to use rand() method, it assigns randomly but not equally, i mean one worker can have more tasks to do than another one. then i’ve tried to use count() method, but couldn’t connect them… I’m new in php and mysql 🙁

i made something like this but only in mysql, but it works only once because of (not in) function.

insert into table_1(worker) 
    select col_1 from table_2 
    where col_1 not in (select worker from table_1) 
    order by col_1 rand() 
    limit 0,1;

Thanks for any help 🙂

Answer 1

I have 2 solutions for you. The first is simpler, but only if you can modify table_2 to add a field for the number of tasks currently assigned. It would be a counter that you would initialize to 0 and then increment every time you assign a task. If you can modify your table, this would select a worker that has the fewest tasks assigned:

select worker_id, MIN(tasks_assigned)
FROM table_2
GROUP BY worker_id

This is a round robin assigner, but it isn’t all that random. I would think equitable assignments is more important though. If you can’t alter your tables, the same solution is a bit more messy:

CREATE TEMPORARY TABLE task_list
( worker_id INT,
  tasks_assigned INT )

SELECT INTO task_list
  SELECT worker_id, count(worker_id) AS tasks_assigned
  FROM table_1
  GROUP BY worker_id

SELECT INTO task_list
  SELECT worker_id, 0 
  FROM table_2
  WHERE worker_id NOT IN (SELECT worker_id FROM task_list)

SELECT worker_id MIN(tasks_assigned) 
FROM task_list
GROUP BY worker_id  

Obviously this isn’t the entire solution. But this will give you a worker_id that has the fewest number of tasks assigned. You’ll then have to use this id to do an update to your task table (table_1)