设置a1在a和b1在b和c1在c等

Question

I have a MySQL table with images data. My backend app is using a live sorting module (drag & drop images).

What I want is to update within a single query all sorted images after sorting process is done, instead of updating single query each time I drop image to a new position (I need to disable any connections while sorting).

As for now, I made this using a foreach loop. Compare two arrays - one that holds the original order of the files, and the second one that holds the new order. When the sorting is done it updates only the images with different order. But I'm not sure if the loop is a good place for firing multi-queries (with many images this could drastically overload app)

public function setSortFilesinSql($new_sort_arr)
{
    $sql = new sql();
    $sql->sqlConnect();
    foreach ($new_sort_arr as $key=>$value){
        if($this->_original_sort[$key] != $value){
            $sql->query("UPDATE images SET sort='".$key."' WHERE name='".$value."' AND full_path='".$this->path."'");
        }
    }
    $this->_original_sort = $new_sort_arr;
    $sql->disconnect();
}

Is there any way to "simlify/speedify" the whole process, or set this as a single query?

---

EDIT

I've checked CASE clause like this:

public function setSortFilesinSql($new_sort_arr)
{
    $sql = new sql();
    $sql->sqlConnect();
    $sort_query = "UPDATE images SET sort = CASE CONCAT(full_path, '/', name)";
    foreach ($new_sort_arr as $key=>$value){
        if($this->_original_sort[$key] != $value){
            $sort_query .= "WHEN '".$this->path."/".$value."' THEN '".$key."' ";
        }
    }

    $sort_query .= "ELSE sort END CASE";
    $sql->query($sort_query);
    $this->_original_sort = $new_sort_arr;
    $sql->disconnect();

}

Query above gives me following error:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CASE'

Answer 1

I just write the SQL part, you can build it from PHP:

UPDATE images
SET sort = CASE name
    WHEN 'x' THEN 1
    WHEN 'y' THEN 2
    ...
    ELSE sort
    END
WHERE full_path='...';

Additionally you can filter the rows in the WHERE clause with AND name in ('x', 'y') . In this case you can save the ELSE part in the CASE .

If you want to use more than one column to identify your row, use this:

UPDATE images
SET sort = CASE CONCAT(full_path, '/', name)
    WHEN 'path/x' THEN 1
    WHEN 'path/y' THEN 2
    ...
    ELSE sort
    END