Group By and displaying entries under date and display count

Question

Here's my data:

id date  
1 2009-01-01 10:15:23  
2 2009-01-01 13:21:29  
3 2009-01-02 01:03:13  
4 2009-01-03 12:20:19  
5 2009-01-03 13:01:06 

What I'd like to do is group by each date and then list the id numbers below each date. I also want to list the count of ids per date.

so my output would look like:

2009-01-01  - Count:2
1  
2   
2009-01-02  - Count:1
3  
2009-01-03  - Count:2
4  
5  

I have the following code that works, but need help changing the logic to display the count.

$query = "SELECT DATE(date) as mydate, id FROM your_data_table ORDER BY mydate, id";
$result = $pdo->query($query);

$oldDate = false;
while ( list($date, $id) = $result->fetch(PDO::FETCH_NUM) ) {
    if ( $oldDate != $date ) {
        echo "$date\n$id\n";
        $oldDate = $date;
    } else {
        echo "$id\n";
    }
}

Answer 1

If you don't mind letting the DB do all the job, and maybe parse the result, an easy way to do is:

SELECT DATE(date) as mydate, COUNT(id) as num, GROUP_CONCAT(id SEPARATOR ",") as ids
FROM your_data_table
GROUP BY DATE(date)
ORDER BY mydate

Maybe needs some work (hadn't tested it).

Answer 2

For the group totals to be done automatically by MySQL, you'd need to use the ROLLUP option. But the query results would still need some client-side massaging to properly display the appropriate divisions when switching from one group to the next.

Answer 3

you can do something like this :

$query = "SELECT DATE(date) as mydate, id FROM your_data_table ORDER BY mydate, id";
$result = $pdo->query($query);

$datas = array();
while(list($date, $id) = $result->fetch(PDO::FETCH_NUM)) {
  if(! isset($datas[$date]) $datas[$date] = array();
  $datas[$date][] = $id;
}

foreach($datas as $date => $ids} {
    echo $date.' - Count: '.count($ids)."\n";
    foreach($ids as $id) {
        echo $id."\n";
    }
}