LeetCode 0196 - Delete Duplicate Emails

Delete Duplicate Emails

Desicription

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

代码语言：javascript复制

 ---- ------------------ 
| 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:

代码语言：javascript复制

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

Solution

代码语言：javascript复制

# Write your MySQL query statement below
DELETE
    P1
FROM
    Person P1, Person P2
WHERE
    P1.Email = P2.Email AND
    P1.Id > P2.Id

sql email rows table unique

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