难度: Easy
原题连接
内容描述
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 | [email protected] |
| 2 | [email protected] |
| 3 | [email protected] |
+----+------------------+
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 | [email protected] |
| 2 | [email protected] |
+----+------------------+
Note:
Your output is the whole Person table after executing your sql. Use delete statement.
思路 1
delete p1 from Person p1, Person p2 where p1.Email = p2.Email and p1.Id > p2.Id