如果使用count和group by

Question

下面给出的是我按日期为每个产品组选择count（product_names）后得到的数组。

Array
( [2019-05-16] => Array
        (
            [0] => 1
        )
    [2019-05-17] => Array
        (
            [0] => 2
        )
    [2019-05-18] => Array
        (
            [0] => 1
        )
    [2019-05-19] => Array
        (
            [0] => 2
            [1] => 1
        )
)

输出应该是这样

Array
(
    [2019-05-16] => Array
        (
            [0] => 1
            [1] => 0
        )
    [2019-05-17] => Array
        (
            [0] => 2
            [1] => 0
        )
    [2019-05-18] => Array
        (
            [0] => 1
            [1] => 0
        )
    [2019-05-19] => Array
        (
            [0] => 2
            [1] => 1
        )
    [2019-05-20] => Array
        (
            [0] => 0
            [1] => 0
        )
)

下面是我用来从数据库获取数据并将其转换为数组的脚本

foreach ($productid as $itemid) {

  $query1 = "SELECT date,COUNT(product_name) AS count FROM app_product_details WHERE date BETWEEN '2019-05-16 00:00:00' AND '2019-05-20 23:59:59' and appid = $itemid GROUP BY date";

        $getquery1 = mysqli_query($conn,$query1);
        while($getcount1 = mysqli_fetch_assoc($getquery1))
        {

          $grset1[] = $getcount1;

        }
      }

 foreach($grset1 as $r){
$dates1[$r['date']][] = $r['count'];

}

我尝试使用COALESCE和IFNULL，但是它不起作用。给出相同的输出而不是零。