Magento:锁定不起作用的自定义MySQL查询

last_used 现场。

查询在phpMyAdmin中运行得非常好,但在Magento中失败。我得到以下错误:

SQLSTATE[HY000]: General error

#0 /var/www/virtual/magentodev.com/htdocs/lib/Varien/Db/Adapter/Pdo/Mysql.php(249): PDOStatement->fetch(2)

以下是我的模型代码,包括SQL查询:

$write = Mage::getSingleton('core/resource')->getConnection('core_write');

$sql = "LOCK TABLES mytable AS mytable_write WRITE, mytable AS mytable_read READ;
        SELECT @val := unique_field_to_grab FROM mytable AS mytable_read ORDER BY last_used ASC LIMIT 1;        
        UPDATE mytable AS mytable_write SET last_used = unix_timestamp() WHERE unique_field_to_grab = @val LIMIT 1;
        UNLOCK TABLES;
        SELECT @val AS val;";

$result = $write->raw_fetchrow($sql, 'val');

raw_query 和 query 而不是 raw_fetchrow 没有运气。

编辑 :我开始认为这可能与PDO驱动程序有关,Magento肯定在使用这个驱动程序。我认为phpMyAdmin正在使用mysqli,但我不能证实这一点。