更新事物列表，而无需点击所有条目 [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可以订购的列表.
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order by order_value.
On load from the database, I simply order by order_value.
通过拖放，他应该可以移动apples，使其出现在列表的顶部.
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.因此，现在在内部，我必须更新每个列表项！如果列表包含20或100个项目，那么对于简单的拖动操作来说，这是很多更新.
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
我只希望进行一次更新.我想到的一种方法是，内部订单"是否为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
在执行拖放n'操作之后，我指定apples的值小于它出现在以下项之前的值:
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
..如果将某个项目拖到中间的某处，则它的order_value大于它在..之后出现的项目.在这里，我将orange移到了salad和mango之间:
.. 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
有什么更好的方法吗?
推荐答案
I ended up using an adjacencies table. I didn't know about it at the time.
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