Postgres 获取电子邮件域的数量

Question

如果我的数据库中有用户电子邮件条目，并且我想查看有多少用户拥有域@gmail.com以及有多少用户拥有域@yahoo.com等等。 这样做的最佳方法是什么？

现在我正在通过执行以下操作来手动一一运行查询：

select email from "user" where email ilike '%@gmail.com';

Answer 1

我的第一个想法是通过以下方式提取域和组：

select substring(email from '@(.*)$') as domain, count(*)
from "user"
group by domain

Answer 2

这是另一种方法：

select dm.domain, count(*) as total
from (
         select lower(right(email, char_length(email) - position('@' in email))) as domain
         from "user"
         group by  domain, email)dm
group by dm.domain
order by total desc

Answer 3

在这种情况下，可以使用函数split_part ：

select split_part(email, '@', 2) "domain", count(*)
from emails 
group by "domain";

PostgreSQL split_part 小提琴

Answer 4

select substring(email from '@(.*)$') as domain, count(*)
from  pytest.emps
group by domain

SELECT distinct(split_part (email,'@',2) ) as domain_name FROM pytest.emps 

SELECT split_part (email,'@',2) as domain_name FROM pytest.emps group by domain_name