我不知道/分组？有？子查询？我可以使用什么？

Question

select seq from a where link != 1 

seq | link
1   | 1
1   | 0
2   | 0
3   | 1
4   | 0

我希望不在1：2,4中返回seq

Answer 1

SELECT seq
  FROM a
 GROUP BY seq
HAVING SUM(link = 1) = 0;

SQL Fiddle