Question

How to find duplicate questions and delete it?

Comments

What about using related questions list?

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That is very time consuming

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Do you want to keep the oldest question or the newest one? Does any of the duplicates you want to delete have answers?

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I want to delete newest one with answer

Answer 1

I don't really have an elegant solution for this, but something like the following might work (all untested, though, so take it with a grain of salt).

First you need to identify the IDs of the questions you want to keep:

SELECT min(postid)
FROM qa_posts
WHERE type='Q'
GROUP BY title;

Now you can delete answers to duplicate question by deleting posts with type "A" whose parent ID is not in that list:

DELETE FROM qa_posts
WHERE type='A' AND parentid NOT IN (
  SELECT min(postid)
  FROM qa_posts
  WHERE type='Q'
  GROUP BY title;
);

and duplicate questions by deleting post with type "Q" whose post ID is not in that list:

DELETE FROM qa_posts
WHERE type='Q' AND postid NOT IN (
  SELECT min(postid)
  FROM qa_posts
  WHERE type='Q'
  GROUP BY title;
);

Comments

Can I make a plugin with this?

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Probably. If you want to go that route I'd recommend investing some more time into optimizing the queries, though. It should be possible to delete everything with a single query. Also, my answer does not address comments. You may want to consider those too if you make a plugin.