<?php $model = new blogTagPluginModel(); $ids = array_keys($model->query("\n SELECT t.id, COUNT(pt.tag_id) cnt FROM `blog_tag` t \n LEFT JOIN `blog_post_tag` pt ON t.id = pt.tag_id\n GROUP BY t.id\n HAVING cnt = 0\n ")->fetchAll('id')); if ($ids) { $model->deleteById($ids); }