MySQL：使用同一表中列的MAX值插入新记录

Question

I need to INSERT a new record, using the MAX value of the position column plus one, in the newly inserted row. So if the MAX value is 14, the next inserted row's position column value should be 15.

This is my current code, which is working but it needs 2 separate queries:

# get position order
$sql = 'SELECT MAX(position) FROM store_item_photo WHERE id_item = 3';
$stmt = cnn()->prepare($sql);
$stmt->execute();
$position = $stmt->fetchColumn();
$position++;

# photo: new record
$sql = 'INSERT INTO store_item_photo (id_item, position) VALUES (3, :position)';
$stmt = cnn()->prepare($sql);
$stmt->bindValue(':position', $position, PDO::PARAM_INT);
$stmt->execute();

I wanted to know if there is some way to achieve the same result with just one query:

# photo: new record (one query)
$sql = 'INSERT INTO store_item_photo (id_item, position) VALUES (3, (SELECT MAX(position) FROM store_item_photo WHERE id_item = 3) + 1)';
$stmt = cnn()->prepare($sql);
$stmt->execute();

That test is throwing an error. Is it possible to achieve this with a similar approach?

I built the schema in sqlfiddle: http://sqlfiddle.com/#!9/228058/1

Answer 1

If you want to use a subquery in an Insert you don't have to use VALUES

Try this query:

INSERT INTO store_item_photo (id_item, position)
  SELECT
    3 AS id_item,
    MAX(position) + 1
  FROM store_item_photo 
  WHERE id_item = 3;

Answer 2

Try this query :

 $sql = 'INSERT INTO store_item_photo (id_item, position) VALUES (3, ((SELECT MAX(position) FROM store_item_photo WHERE id_item = 3) + 1))'; $stmt = cnn()->query($sql);