I recently added a lot of data to a drupal site by running some scripts that I'd created in php. This was to save me the time of manually capturing the content. After successfully adding the content, when I tried to add a new content item, I got the following error:
Warning: Duplicate entry '503-503' for key 1 query: INSERT INTO node (nid, vid, title, type, uid, status, created, changed, comment, promote, moderate, sticky) VALUES (503, 503, 'World Bank ', 'content_organisation', 1, 1, 1171017191, 1171017191, 2, 1, 0, 0) in It turns out that Drupal uses the sequences table to keep track of what the highest id in certain tables is. I had forgotten to update this table with the id of the most recent node that I'd added.