如何实现标签计数 | 如何实现标签计数

本文介绍了如何实现标签计数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有我的标签在我的数据库desinged是这样的：

I have my tags desinged like this in my database:

Table: Item
Columns: ItemID, Title, Content

Table: Tag
Columns: TagID, Title

Table: ItemTag
Columns: ItemID, TagID



//example -- this is the right sidebar of stackoverflow
c# × 59279
sql × 14885
asp.net-mvc × 9123
linq × 4337
tags × 339

如果我想知道每个标签的数量，如计算器如何计算自己的标签我会怎么做呢？我将执行什么样的查询。我打开这两个常规的SQL和LINQ

if I wanted to know the count of each tag such as how stackoverflow counts their tags how would I do it? What kind of query would I perform. I am open to both regular sql and linq

推荐答案

添加在作为抗衡工作表标签另一列。当您添加或删除的项更新计数器标签（换句话说，如果加上Itemtag连续递增变量表计数器，当删除递减计数器）

Add another column in the table Tag that work as counter. When you add or remove a tag from an item you update the counter (in other words, when add a row on Itemtag increment the counter on Tag table, when remove decrement the counter)

标签添加到项目：

INSERT INTO Itemtag (itemid,tagid) VALUES ('$itemid','$tagid');
UPDATE Tag SET counter=counter+1 WHERE tagid='$tagid';

从项目中删除标签

remove tag from item

DELETE FROM Itemtag WHERE itemid='$itemid' AND tagid='$tagid';
UPDATE Tag SET counter=counter-1 WHERE tagid='$tagid';

检索与反项目代码

retrieve item tags with counter

SELECT t.title, t.counter FROM Itemtag AS it JOIN Tag AS t ON t.idtag=it.tagid
WHERE it.itemid='$itemid'

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