刚刚开始学习 sql，碰上一个问题自己解决不了

应该要有 count

select
author,
ab_num
from (
select author, count(album) as ab_num
from table_cd
group by author
) t where ab_num > 1

@ggjjl1 谢谢您

如果再加一个要求，不能用子查询：

SELECT t1.author
FROM tb AS t1
JOIN tb AS t2 ON t1.author = t2.author
AND t1.id != t2.id
GROUP BY author

`id` 是表的主键

@elvba 弱弱的问一下，这样写不会出笛卡尔乘积么？

@ggjjl1 会的……