fernandobasso / crud-custom-position

A CRUD that allows the user to manually set the position in which posts are to be listed.

Crud With Custom Position

This is a solution to a situation I had at work. The basic idea is that the user wants to define the position an entry on the database should appear on the web page by providing a number.

Add New Entry

In this case, if the new position is set to zero, we assume the user wants to insert at the end. We then get the number or rows and set the position to number of rows + 1.

Lower to Upper Position

If user updates position 5 to 1 (it goes from a lower position to a higher position), we first update the one that current has position 1 to 2, and also increment the other positions stopping at the item that has the position 1 less than the one we are changing. Finally we update the item that the user is explicitly changing by its id.

// Updates from $newpos up to before $oldpos.
$sql = "UPDATE post SET
  pos = pos + 1
  WHERE post.pos >= $newpos
  AND post.pos < $oldpos;";


// Change the pos the explicitly repositioned post itself.
  $sql = "UPDATE post SET
  pos = {$newpos}
  WHERE post.id = {$pk};";

Upper to Lower Position

Update from current item pos + 1 up to the one in the position that the changed one will occupy. If user changes item in position 4 to position 1, decrement from position 2 to the one that current is in position 4. Then, update the item that the user is explicitly changing by its id.

// Updates from $pos + 1 to the one that will be changed explicitly.
$sql = "UPDATE post SET
  pos = pos - 1
  WHERE post.pos = $newpos + 1
  AND post.pos <= $oldpos;

// Change the position of the explicitly repositioned post itself.
$sql = "UPDATE post SET
  pos = $newpos
  WHERE id = {$pk};";

Remove Entry

Simply decrement the position of all the entries whose position are greater than the position of the element being removed.