如果未使用MySQL IN语句从数组中找到匹配项，则返回0

Question

I know there are many similar questions and answers, but none of them are working in this case, as I'm using IN statement to get matches from array and my dates are in varchar data type because of its format. Here it is:

I'm trying to check if array items exists in database and get the count for each of them as an array. My SQL query runs fine and gets the results, but the only problem is that I want it to return 0 for array items that does not exist in a database instead of skipping it.

So for example here is my database table:

postId   reactedTo   reactedDate
126      Like        22 Jun 2019
172      Haha        24 Jun 2019
172      Wow         27 Jun 2019
132      Like        27 Jun 2019

Here is my function to run the SQL Query and get the results as an array

public function reactionsAnalytics() {
    global $wpdb;
    $tableName = $wpdb->prefix.'reactions';
    $dates = $this->getLastNDays(7); //array('22 Jun 2019', '23 Jun 2019', ... ,'28 Jun 2019');
    $reacts = $wpdb->get_results("
SELECT reactedDate, count(*) AS count
  FROM {$tableName} 
 WHERE reactedDate IN ('".implode("','", $dates)."')  
 GROUP 
    BY reactedDate
", ARRAY_A);

    $result = array();
    foreach ($reacts as $react) {
        $result[] = $react['count'];        
    }

    wp_die(json_encode($result));
}

The expected outout of this function is ["1","0","1","0","0","2","0"], but I'm getting ["1","1","2"]. How can I prevent the $reacts query from skipping not found items and make it output 0 instead?

I've tried using COALESCE , IFNULL and SUM in various variations but got same results without zeroes.

Here is the SQL Fiddle and you can play with it:

http://sqlfiddle.com/#!9/ffbb98/5

Thanks!

Answer 1

Instead of trying to complicate the query, you simply need to change your application (PHP) code slightly. Get the query results for the dates available in the DB. Now, in PHP code, simply check if the count is available for the date or not. If yes, use the count, else set as zero.

// Change the SQL query result to an array with date as key, and count as value
$reacts_mod = array_combine(array_column($reacts, 'reactedDate'), 
                            array_column($reacts, 'count'));

// Now prepare the $result
$result = array();
// Loop over input dates here
foreach ($dates as $dt) {

    // If you have count obtained from the query result, then consider that else 0
    if ( isset($reacts_mod[$dt]) ) {
        $result[] = $reacts_mod[$dt];
    } else {
        $result[] = 0;
    }

    // Note: PHP7 code would be simply:
    // $result[] = $reacts_mod[$dt] ?? 0;
}