问题
编写一个 SQL 查询,查找 Person 表中所有重复的电子邮箱。
示例:
Id | |
---|---|
1 | a@b.com |
2 | c@d.com |
3 | a@b.com |
根据以上输入,你的查询应返回以下结果:
a@b.com |
说明:所有电子邮箱都是小写字母。
准备
create database leecote182;
use leecote182;
create table Person(
Id int(10),
Email varchar(20));
insert into Person values
(1,'a@b.com'),
(2,'c@d.com'),
(3,'a@b.com');
解答
#方法一:
select Email from
(
select Email, count(Email) as num
from Person
group by Email
) as statistic
where num > 1
;
#方法二:
select Email
from Person
group by Email
having count(Email) > 1;
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