sql-Count应该只有一个和两个

Question

我需要编写查询

select count(*) cnt from tabel1,table2
where table1.a=table2.b

显示计数为0 1 2

通过使用上面的查询作为子查询我需要从表1中获取id，其中count应该只有1和2.它不应该为零。

请建议

Answer 1

试试这个

select a.a , count(b.b) 
from table1 a 
join table2 b
on a.a = b.b
group by a.a
having count(b.b) > 0

Answer 2

请尝试：

select a.id , count(*) 
from table1 a join table2 b
  on a.id = b.id
group by a.id
having count(*)  IN (1, 2)