不想写第二遍的刷题笔记

世界级打野都是rush大龙的

Delete Duplicate Emails

LeetCode 196

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 |
+----+------------------+

Note:

Your output is the whole Person table after executing your sql. Use delete statement.

Solution

delete from Person
where Email in
(select * from
(select Email from Person group by Email having count(Email) > 1) a)
and Id not in
(select * from
(select min(Id) from Person group by Email having count(Email) > 1) b)