What do I mean "tags related to tags" list?   We think that there are 3 tags in the article (A, B), (A, C), (B, C) etc. A, B, C. / P>   Table: Tag     tag_ id tag_title tag_title     Table: Tag 2 article   We can add a more table in which there is article_id and it is MD5 (A, B, C). Before hashing, we should sort the tags by the alphabet.    Table: article_tags_hashed     id article_id md5 count    This table gives us the tag (A, B , C) will help find articles with the exact set, but it will not only help to find articles containing (A, B), (A, C), (B, C)   most What is good practice?   PS: Sorry for my english, it's too bad.     I do not think you need  article_tags_hashed  because you have  Tags2articles  group the results for the query and can count.   Example:    Choose tag_id as tag_art tag (article_id) as tags in the tag_id where tag_id (...) tags by tag by article_id  / pre>  Most tagged articles will be placed first.