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Editorial Team
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Asked: 2026-06-03T14:31:16+00:00

I currently have the current MySQL query taking up to 10 seconds to run

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I currently have the current MySQL query taking up to 10 seconds to run in my application:

SELECT tagid, tag FROM tags WHERE tagid IN 
(SELECT DISTINCT tagid FROM news_tags WHERE newsid IN 
(SELECT newsid FROM news_tags WHERE tagid IN (16,32)
GROUP BY newsid HAVING COUNT(newsid)>=2)) 
AND tagid NOT IN (16,32) ORDER BY level, tagid

The tables used are:

  • table news_tags, with columns newsid, tagid
  • table tags, with columns tagid, tag, level

The purpose of the query is to find “news” items which have been tagged with tags with tagid 16 and 32, then find other tags these news items have also been tagged with, for the purposes of allowing a user to further narrow down the “news” items with more specific tag combinations. The ultimate goal is to grab the remaining relevant tag and tagid columns from the tags table.

I have tried different attempts at an equivalent JOIN but have failed to select all remaining tagids on the news items which have the provided tags attached to them.

Here is my EXPLAIN SQL results, in case they point to another cause of slowness which I’m missing:

id|select_type       |table    |type          |possible_keys|key    |key_len|ref |rows|Extra
 1|PRIMARY           |tags     |range         |PRIMARY      |PRIMARY|      4|NULL|  55|Using where; Using filesort
 2|DEPENDENT SUBQUERY|news_tags|index_subquery|tagid        |tagid  |      4|func|  26|Using index; Using where
 3|DEPENDENT SUBQUERY|news_tags|index         |tagid        |PRIMARY|      8|NULL|  11|Using where; Using index

Just to clarify the problem: I wanted remaining tags for news items tagged with BOTH tags 16 and 32, not either 16 or 32. Sorry for any confusion.

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1 Answer

  1. Editorial Team
    SELECT DISTINCT tags.tagid, tags.tag
FROM
       tags                             -- tags from the ...
  JOIN news_tags AS n0 USING (tagid)    -- ... news items tagged with ...
  JOIN news_tags AS n1 USING (newsid)   -- ... tagid = 16 and ...
  JOIN news_tags AS n2 USING (newsid)   -- ... tagid = 32
WHERE
  n1.tagid = 16 AND n2.tagid = 32
  AND tags.tagid NOT IN (16,32)         -- not the tags we already know about
ORDER BY tags.level, tags.tagid
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