How to merge joomla tag using SQL query from phpMyadmin?

Question

Since Joomla does not have a tag merging feature, I'm looking for a way to merge existing tags using SQL query in phpmyadmin.

• Old tag_id=1
• New tag_id=2

This query works as long as all of the articles that have the tag_id=1 don't have also the tag tag_id=2.

Update xxx_contentitem_tag_map SET tag_id=2 WHERE tag_id=1

But it doesnt work when one of the article also have the tag_id=2. So I'm looking for a smart query that would work only on that selection:

SELECT * FROM xxx_contentitem_tag_map WHERE tag_id=1 AND tag_id!=2

How should I merge this SELECT query with the update query?

Answer 1

Try this, but please backup your database before:

UPDATE
  xxx_contentitem_tag_map
SET
  tag_id = 2
WHERE
  tag_id = 1 AND 
  core_content_id NOT IN (
    SELECT 
      core_content_id 
    FROM 
      xxx_contentitem_tag_map 
    WHERE
      tag_id = 2
  )

Basically you have to select all article IDs where the tag ID is already 2 and then exclude them from your update query by using the NOT IN operator