在包含来自SQL查询的数据的表中对NON-SQL表列进行排序

Question

Below I have stripped down my code to a simplified version. I am storing SQL SELECT results for:

• last name (dlname)
• category (category)
• date this data was added to database (date_added)
• clients name (client)

I have appended an additional field outside the SQL SELECT called 'days_on_list'. This field shows the number of days since the data was added to the database, making the table output 5 columns of user data. ALL 5 COLUMNS ARE TO BE SORTABLE.

I am using server-side JSON and have successfully been able to display this to the table and perform sorting on 4 of the 5 columns. The problem is that I am unable to sort the 'days_on_list' field as the PHP file containing the SQL code only allows me to sort the 4 fields from the select query . Is there a way I can make 'days_on_list' column be sortable in the table? I know I can add this field to the sql table, but I would have to run a scheduled event on the server to update this daily (which I am not comfortable with).

Is there another way to allow for this kind of flexible table sorting?

Sorry about the question title (may be confusing), I was having trouble putting this into a question.

 /*SQL CODE ABOVE HERE STORES SELECT RETURNS IN $result*/ $cart = array(); $i = 0; //index the entries // get variables from sql result. if ($num_rows > 0) { //if table is populated... while ($row = mysqli_fetch_assoc($result)) { //calculate days on list by getting the number of days from //the 'date_added' to today $date1 = date_create($row['date_added']); $today = date_create(date("dmY")); $interval = date_diff($date1, $today); $doty = $interval - > format("%a"); $cart[$i] = array( "dlname" => htmlspecialchars($row['dlname']), "category" => htmlspecialchars($row['category']), "date_added" => htmlspecialchars($row['date_added']), "client" => htmlspecialchars($row['client']), "days_on_list" => $doty, //date_added to now ); $i = $i + 1; //add next row } //encoding the PHP array $json_server_pagination_data = array( "total" => intval($num_rows), "rows" => $cart, //array data ); } echo json_encode($json_server_pagination_data); 

Answer 1

Because days_on_list is calculated by simply comparing date_added to the current date, sorting by days_on_list should have exactly the reverse effect as sorting by date_added .

In other words, you don't actually need to sort by days_on_list . If the user selects days_on_list as the sort column, just use ORDER BY date_added (in the opposite direction ASC/DESC).