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Remove parent tags from a post where a child tag is present


With the hierarchical tags, it would be possible to have both a tag and its parent on the same post which is means that the parent tag is unneeded. An example would be a post with both an animal and a deer tag on Outdoors.

Rather than manually removing the parent tags from these posts, it should be possible to do it with a SQL statement.

If I understand the schema right, this should select posts where this happens,

SELECT post_id 
FROM posts_tags pt1
JOIN tags t1 on pt1.tag_id =
JOIN tags t2 on = t2.parent_id
JOIN post_tags pt2 on pt1.post_id = pt2.post_id and pt2.tag_id =

To remove the relationships, simply replace the select with


assuming the SQL is correct.

Why should this post be closed?


Is this a one-time request for existing posts, or a request for this to happen automatically for all new questions? ‭‮edoCfOtrA‭ 2 months ago

@Artofcode To me this would be ongoing, to me the point of hierarchical tags was to remove the need to ever tag a post with both the parent and the child tags. ‭Charlie Brumbaugh‭ 2 months ago

@CharlieBrumbaugh In that case, I think I agree with msh210's answer - it seems that there are cases where both tags could apply. Let's see what others think. As an alternative, it might be possible to add a warning - check the tags before posting the question, and alert the author if both a parent and a child tag are in use. ‭‮edoCfOtrA‭ 2 months ago

If asking for automatic removal of parent where child is present and if editing in a parent where child is present seems odd? ‭pnuts‭ 2 months ago

1 answer


It's not always correct to remove a parent tag, and therefore such removal should probably not be done automatedly — or, at least, if it is done automatedly, should be sensitive to human intervention so it doesn't re-remove a tag that someone has re-added after automated removal. For example, if mammal is a parent of deer, but a question is about how non-deer mammals in general and deer in particular get along with one another, you'd probably want both tags.


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