leetcode_sql_4，196

196. Delete Duplicate Emails

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]  |
+----+------------------+

 

# Write your MySQL query statement below
DELETE P
FROM Person P,Person P1
WHERE P.Id>P1.Id AND P.Email=P1.Email;

 

 

转载于:https://www.cnblogs.com/coskaka/p/7137461.html