/**
* Lock the selected rows in the table for updating.
* 悲观锁 锁住后读改阻塞
* @return $this
*/
public function lockForUpdate()
{
    return $this->lock(true);
}

/**
* Share lock the selected rows in the table.
* 共享锁 锁住后能读 修改阻塞
* @return $this
*/
public function sharedLock()
{
    return $this->lock(false);
}