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[LeetCode] Delete Duplicate Emails 删除重复邮箱

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 |…

LeetCode - Delete Duplicate Emails

Discription:Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. 删除重复的Email地址,保留Id最小的那个. 使用自身连接循环即可. # Write your MySQL query statement below delete p1 from Person p1, P…

LeetCode——Delete Duplicate Emails（巧用mysql临时表）

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 |…

Leetcode 182. Duplicate Emails

Write a SQL query to find all duplicate emails in a table named Person. +----+---------+ | Id | Email | +----+---------+ | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | +----+---------+ For example, your query should return the following for the abov…

LeetCode Database: 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 | john@example.com | | 2 | bob@example.com |…

leetcode【sql】 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 | john@example.com | | 2 | bob@example.com |…

LeetCode DB : 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 | john@example.com | | 2 | bob@example.com |…

leetcode 196. Delete Duplicate Emails 配合查询的delete

https://leetcode.com/problems/delete-duplicate-emails/description/ 题意要对原来的数据表进行删除,不删除不行,它每次只输出原来那个表. 所以我一直用select测试,这样是永远都不行的. 首先应该对join或者子查询要熟悉,即使不会删除,也要知道怎样选出不合法.合法的出来. 特别注意的是,数据库的,你from什么表,那么就只能对那个表进行改动. 所以如果是from one join two,那个这个是一个新的临时表,需要改名后才能…

LeetCode 196. Delete Duplicate Emails (删除重复的电子邮箱)

题目标签: 题目给了我们一个 email 的表格,让我们删除重复的. 建立Person p1,Person p2,当email 相同时,而且 p1 id 要大于 p2 id 时候,删除这一行. Java Solution: Runtime:  869 ms, faster than 33 % Memory Usage: N/A 完成日期:06/01/2019 关键点:p1.Id > p2.Id # Write your MySQL query statement below DELETE p1…

leetcode 196. Delete Duplicate Emails

# 慢,内连接delete p1 from Person p1, Person p2 where p1.Email=p2.Email and p1.Id>p2.Id delete from Person where Id not in ( select Id from ( select min(Id) as Id from Person group by Email) p);…