1. 找到所有分类（标签同理）

SELECT mid FROM typecho_metas AS m WHERE m.type = 'category';

2. 找到分类关系表，统计文章数

SELECT r.mid,
       count(cid)
FROM typecho_relationships as r
WHERE r.mid IN
    (SELECT mid
     FROM typecho_metas AS m
     WHERE m.type='category')
GROUP BY r.mid;

3. 提取出分类名称

SELECT r.mid,
       m.name,
       count(cid)
FROM typecho_relationships as r
LEFT JOIN typecho_metas as m ON m.mid=r.mid
WHERE r.mid IN
    (SELECT mid
     FROM typecho_metas AS m
     WHERE m.type='category')
GROUP BY r.mid;

4. 以上一个查询为基础修改原始表metas

UPDATE typecho_metas,
  (SELECT r.mid AS mid,
          count(cid) AS COUNT
   FROM typecho_relationships AS r
   WHERE r.mid IN
       (SELECT mid
        FROM typecho_metas AS m
        WHERE m.type='category')
   GROUP BY r.mid) AS tmp
SET typecho_metas.COUNT = tmp.COUNT
WHERE tmp.mid = typecho_metas.mid;

参考链接：https://blog.phpgao.com/typecho_delete_category_mistake.html