简单的SQL语句~~~谁帮我写阿 谢谢

Question

select nvl(max(字段B),0) from 表名 group by 字段A

Answer 1

B字段的值不是连续的 我想查的是件数 count()

Answer 2

select 字段A,sum(decode(字段B,null,0,1)) from 表名 group by 字段A

Answer 3

select a,sum(decode(nvl(b,0),0,0,1)) from tablename group by a

Answer 4

select a,count(b) from tablename group by ab为NULL时,COUNT(B)为0.所以可以直接这么写.