SELECT id,title FROM a WHERE title IN ( SELECT title FROM a GROUP BY title HAVING COUNT(title)>1) ORDER BY title查询a表中title有重复的数据 title为VARCHAR类型 查询出数据1000多条 需要16秒 很慢。 不管在后面加不加上LIMIT X 都是很慢的 哪怕只取LIMIT 10 求优化!
调试欢乐多
SELECT id,title FROM a WHERE not exists(select 1 FROM a WHERE
a.title=title and a.id<id)
SELECT id,title FROM a WHERE EXISTS (SELECT 1 FROM a temp WHERE temp.title = a.title
AND temp.id<> a.id) ORDER BY title
我这样写好了 请问如何? 大概3秒。尚可接受