Database PDOException after INSERT

Hi, constantly I'm receiving the error: PDOException: SQLSTATE[HY000]: General error after execute an INSERT using the db::query method.

This is part of the code I'm using:

$params = array(
  ':purchaseId' => '123456789',
  ':sku'        => '123456789',
  ':date'       => '2015-11-19 00:00:00'
);

$query = "INSERT INTO links 
  SET purchase_id = :purchaseId, 
      item_id = (SELECT id 
                 FROM   items 
                 WHERE  sku = :sku), 
      date = :date
";

db::query($query, $params);

It does its job in the database perfectly. All is inserted in its tables, nevertheless it always throws the error PDOException: SQLSTATE[HY000]: General error. I sought in the class lib/database.php#L318 and I think that the issue could be related with the method fetchAll as is mentioned in this message http://stackoverflow.com/a/12980031/1668897

Important: I've checked the methods: db::lastQuery(), db::lastId() are fine after the error, where lastId() gives the last inserted id. Also db::lastError() returns a null value.

What can I do? or Is there a different way to execute a query with a subquery without use the db::query() method?

getkirby-v2 / toolkit

Database PDOException after INSERT #116