Question

我试图从我的列表中仅选择唯一的电子邮件。这是我的数据库的一个例子

1 john@email.com unpaid newspaper
2 Emily@email.com paid magazine
3 terry@email.com unpaid magazine
4 john@email.com paid magazine

问题是，如果我使用SELECT DISTINCT WHERE payment = paid，john就会出现。当我付款=未付款时，约翰也会出现。我只想选择具有良好付款历史（没有未付款）的客户。我该如何解决这个问题？

Answer 1

您还可以使用sum与表达式payment = 'unpaid'来获取没有unpaid个条目的电子邮件

select email
from table1
group by email
having (sum(payment = 'unpaid')) = 0

DEMO

Answer 2

您可以使用exists运算符：

SELECT DISTINCT email
FROM   mytable a
WHERE  NOT EXISTS (SELECT *
                   FROM   mytable b
                   WHERE  a.email = b.email AND b.payment = 'unpaid')

Answer 3

使用subselect尝试not in：

select * from `table` where payment='paid' and user not in (select user from `table` where payment='unpaid')

MySQL选择distinct，没有重复

3 个答案: