选择与多个标签匹配的项目 [英] Selecting an item matching multiple tags

问题描述

这似乎很基础，但我无法弄清楚.

This seems very basic but I can't figure it out.

我有一个表"item_tags"，我想选择所有与标签1和2匹配的项目(例如，每个项目必须同时具有两个标签).

I've got a table "item_tags", and I want to select all of the items that match tags 1 and 2 (as in, each item has to have both tags).

我该如何在mysql中做到这一点?

How would I do this in mysql?

创建表是:

CREATE TABLE `item_tags` (
  `uid_local` int(11) NOT NULL DEFAULT '0',
  `uid_foreign` int(11) NOT NULL DEFAULT '0',
  `sorting` int(11) NOT NULL DEFAULT '0',
  KEY `uid_local` (`uid_local`),
  KEY `uid_foreign` (`uid_foreign`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

谢谢！

推荐答案

使用:

  SELECT i.uid
    FROM ITEMS i
    JOIN ITEM_TAGS it ON it.uid_local = i.uid
                   AND it.uid_foreign IN (1, 2)
GROUP BY i.uid
  HAVING COUNT(DISTINCT it.uid_foreign) = 2

您需要定义GROUP BY和HAVING子句，并且不同标签ID的数量必须等于您在IN子句中指定的标签数.

You need to have a GROUP BY and HAVING clause defined, and the count of distinct tag ids must equal the number of tags you specify in the IN clause.

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