Easy

题目要求用delete语句，思路是自连接，然后删除大于最小id的id所在行 用min（id），group by email也可以

Question

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 |
+——+—————————+

Approach**

  1. DELETE p1 FROM Person p1,
  2.     Person p2
  3. WHERE
  4.     p1.Email = p2.Email AND p1.Id > p2.Id