MySQL的row 20000 was cut by group_concat()问题

SELECT b.* FROM (
SELECT SUBSTRING_INDEX(GROUP_CONCAT(id),',',1) AS id FROM news GROUP BY title
HAVING COUNT(*) > 1 ) a JOIN choice_news b ON a.id = b.id;

SUBSTRING_INDEX(GROUP_CONCAT(id),',',1) 获取以“,”分割的第一个值，但是当group的数据超过1024后，就会出现row 20000 was cut by group_concat()的error

解决方法

SET group_concat_max_len=200000; #此值大于你要分组的数量即可