在不点击每个条目的情况下更新事物列表 [英] Update a list of things without hitting every entry

问题描述

我在数据库中有一个用户应该能够订购的列表.

I have a list in a database that the user should be able to order.

itemname|  order value (int)
--------+---------------------         
salad   |  1
mango   |  2
orange  |  3
apples  |  4

从数据库加载时，我只是按 order_value 排序.

On load from the database, I simply order by order_value.

通过拖放，他应该能够移动apples，使其出现在列表顶部..

By drag 'n drop, he should be able to move apples so that it appears at the top of the list..

itemname|  order value (int)
--------+---------------------         
apples  |  4
salad   |  1
mango   |  2
orange  |  3

好的.所以现在在内部我必须更新每个列表项！如果列表有 20 或 100 个项目，那么对于简单的拖动操作来说就需要很多更新.

Ok. So now internally I have to update EVERY LIST ITEM! If the list has 20 or 100 items, that's a lot of updates for a simple drag operation.

itemname|  order value (int)
--------+---------------------         
apples  |  1
salad   |  2
mango   |  3
orange  |  4

我宁愿只更新一次.我想到的一种方法是内部订单"是否是 double 值.

I'd rather do it with only one update. One way I thought of is if "internal Order" is a double value.

itemname|  order value (double)
--------+---------------------         
salad   |  1.0
mango   |  2.0
orange  |  3.0
apples  |  4.0

所以在拖放操作之后，我指定 apples 的值小于它要出现在前面的项目:

SO after the drag n' drop operation, I assign apples has a value that is less than the item it is to appear in front of:

itemname|  order value (double)
--------+---------------------         
apples  |  0.5
salad   |  1.0
mango   |  2.0
orange  |  3.0

.. 如果一个项目被拖到中间某处，它的 order_value 比它之后出现的那个大.. 这里我将 orange 移动到 <代码>沙拉和芒果:

.. and if an item is dragged into the middle somewhere, its order_value is bigger than the one it appears after .. here I moved orange to be between salad and mango:

itemname|  order value (double)
--------+---------------------         
apples  |  0.5
salad   |  1.0
orange  |  1.5
mango   |  2.0

对更好的方法有什么想法吗?

Any thoughts on better ways to do this?

推荐答案

我最终使用了一个 邻接表.我当时并不知道.

I ended up using an adjacencies table. I didn't know about it at the time.

这篇关于在不点击每个条目的情况下更新事物列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！