【MySQL】【leetcode】 Delete Duplicate Emails解题报告

题目

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

Id	Email
1	john@example.com
2	bob@example.com
3	john@example.com

Id is the primary key column for this table.

For example, after running your query, the above Person table should have the following rows:

Id	Email
1	john@example.com
2	bob@example.com

题目来源：https://leetcode.com/problems/delete-duplicate-emails/

代码

Email重复的话，保留ID最小的那条记录，其余的删除。

#方法一：
# Write your MySQL query statement below
delete from Person
where Id not in (
select * from (
select MIN(Id) from Person group by Email
) as tb
);
#方法二：
# Write your MySQL query statement below
delete p1
from  Person as p1, Person as p2
where p1.Email = p2.Email and p1.Id > p2.Id;