SQL - WHERE AGGREGATE> 1

Question

想象一下,我有一个包含{id,username,firstname,lastname}的客户的数据库表

如果我想找到有多少个不同名字的实例我可以做:

select firstname,count(*) from Customers group by 2 order by 1;

   username | count(*)
   ===================
   bob      |   1
   jeff     |   2
   adam     |   5

如何编写相同的查询只返回多次出现的名字？即在上面的例子中只返回jeff和adam的行.

Answer 1

你想要这个having子句,如下:

select 
    firstname,
    count(*) 
from Customers 
group by firstname
having count(*) > 1
order by 1