如何检索MySQL记录列表中的下一项? [英] How to retrieve the next item in a list of MySQL records?

问题描述

我正在使用Propel与symfony合作，试图为后退和下一个按钮创建功能:

I'm working with symfony using Propel trying to create functionality for back and next buttons:

$c = new Criteria();

$c->add(CartPeer::CATEGORY, $category);
$c->add(CartPeer::ITEM_ID, $item->getItemId(), Criteria::GREATER_THAN);
$c->addAscendingOrderByColumn(CartPeer::ITEM_NAME);

$this->next = CartPeer::doSelectOne($c);

现在，如果项目的标识符按升序排列，则可以正常工作，但通常情况并非如此.

Now, this works fine if the item's identifiers are in ascending order, but usually this is not the case.

如何修改此代码，以便它在返回的记录列表中当前$item之后立即选择项目，而不是选择带有下一个升序数字ID的项目?

How can I modify this code so it selects the item immediately after the current $item in the list of records returned instead of selecting one with the next ascending numerical ID?

示例:

Record: 0 | ItemID: 5
Record: 1 | ItemID: 2
Record: 2 | ItemID: 7 <-- $item
Record: 3 | ItemID: 4 <-- I want this to be $next
Record: 4 | ItemID: 9

推荐答案

我实际上并没有使用Symfony，但是如果您使用的是Propel的远程版本，则可以访问 paginate()方法最终对您可能更好.

I don't actually use Symfony, but if you're using an even remotely recent version of Propel with it then you have access to the paginate() method which may be a lot better in the end for you.

$pager = CartQuery::create()
           ->filterByCategory($category)
           ->orderBy(CartPeer::ITEM_NAME)
           ->paginate($pageToLoad, $resultsPerPage);
foreach($pager as $result) {
  // do something with the record
}
if ($pager->haveToPaginate()) {
  // build some paging items using PropelModelPager methods:
  if (!$pager->isFirstPage()) {
    echo "<a href='?page=".$pager->getPreviousPage()."'>Previous</a>";
  }
  if (!$pager->isLastPage()) {
    echo "<a href='?page=".$pager->getNextPage()."'>Next</a>";
  }
}

如果您确实想按照自己的方式做，则可能要完全消除ItemId的限制，而只需在您的限制中添加一个偏移量即可:

If you really want to do it your way, you may want to eliminate the restriction by ItemId entirely and simply add an offset along with your limit:

// This will be however many results have already been shown (page size?)
$offset = 10;

$c = new Criteria();
$c->add(CartPeer::CATEGORY, $category);
$c->addAscendingOrderByColumn(CartPeer::ITEM_NAME);
$c->setOffset($offset);
$this->next = CartPeer::doSelectOne($c);

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