我不知道/分組？有？子查詢？我可以使用什麼？

Question

select seq from a where link != 1 

---

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

我要的不是1返回序列：2,4

Answer 1

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

SQL Fiddle