Question

I have an array that looks like:

array(
    [0] => 1
    [1] => 2
    [2] => 4
    [3] => 3
)

Currently I am looping over the array and running a single update along the lines of

foreach($array as $position => $id){
   //query = update users set order = ($position+1) where id = $id
}

obviously not the actual code, but it get’s the point across,

If I have 1000 items in my list, that’s 1000 queries,

I was wondering if there was a way to do this all in one query?

Answer 1

You can use the MySQL case statement. I’m not sure whether it would be much faster or not, but here’s how it might work:

$query = 'UPDATE users SET order = CASE id ';
foreach($array as $position => $id) {
    $query .= 'WHEN '.$id.' THEN "'.($position+1).'" ';
}
$query .= 'ELSE order ENDCASE'; // leave order the same if the id doesn't match the array
// run $query...

MySQL CASE Syntax