select records with dates in where condition and group the results based on each date

Question

I have a mysql table as below:

t_id    project_id  task_id  start_date
---------------------------------------
1        29         1       2020-03-09
2        29         2       2020-02-09
3        1          3       2019-02-20
4        1          4       2019-12-09
5        1          5       2019-12-09

I want to show the data from the above table such that all task_id has to be shown as comma-separated-values for a particular date for a particular project. Let's say for project_id=1 I am listing all dates in the start_date first, then I will show the tasks with the same start_date will be listed as comma-separated.

The expected result is:

start_date      task_id
-----------------------
2019-02-20      3
2019-12-09      4,5

I tried the to achieve the same with 2 foreach loops but I'm not getting expected results.Below is my code:

Controller:

$id = $this->uri->segment(4);       
$dates = $this->Timesheet_model->get_tasks_dates($id); //get the dates
foreach($dates as $d)
    {
        $rows = $this->Timesheet_model->get_project_tasks_by_date($id,$d->start_date); //get tasks for each date
            foreach($rows->result() as $res)
            {
                $t[] = $res->task_id;
            }
        $ts = implode(",",$t);
        $tasks = array(
            'date'=>$d->start_date,
            'tasks'=>$ts
        );
    }
    print_r($tasks);

Model

public function get_tasks_dates($id)
{
    $sql = 'SELECT DISTINCT (start_date) FROM xin_tasks WHERE project_id = ? ORDER BY start_date DESC ';
    $binds = array($id);
    $query = $this->db->query($sql, $binds);

    return $query->result();
}

public function get_project_tasks_by_date($id,$d)
{
    $sql = 'SELECT task_id FROM xin_tasks WHERE project_id = ? AND start_date = ?';
    $binds = array($id,$d);
    $query = $this->db->query($sql, $binds);

    return $query;
}

When I try print_r($tasks) the result is Array ( [date] => 2019-02-20 [tasks] => 4,5,3 ) .

I know this is not a complex problem, but at the moment I can't figure out the proper solution to achieve this. Is there any other efficient way to solve this?

Answer 1

SELECT start_date,GROUP_CONCAT(task_id) as task_id
from project
where project_id = 1
group by start_date

Your problem can be achieved using this single query.

Answer 2

Use DISTINCT keyword,if same task_id repeated in a same day.

SELECT start_date,GROUP_CONCAT(DISTINCT task_id) as task_id
FROM project
WHERE project_id = 1
GROUP BY start_date;

If you use DISTINCT ,we will get unique task_id(s)..