Algorithm
Problem Name: 196. Delete Duplicate Emails
Table: Person
+-------------+---------+ | Column Name | Type | +-------------+---------+ | id | int | | email | varchar | +-------------+---------+ id is the primary key column for this table. Each row of this table contains an email. The emails will not contain uppercase letters.
Write an SQL query to delete all the duplicate emails, keeping only one unique email with the smallest id
. Note that you are supposed to write a DELETE
statement and not a SELECT
one.
After running your script, the answer shown is the Person
table. The driver will first compile and run your piece of code and then show the Person
table. The final order of the Person
table does not matter.
The query result format is in the following example.
Example 1:
Input: Person table: +----+------------------+ | id | email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com | | 3 | john@example.com | +----+------------------+ Output: +----+------------------+ | id | email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com | +----+------------------+ Explanation: john@example.com is repeated two times. We keep the row with the smallest Id = 1.
Code Examples
#1 Code Example with SQL
Code -
SQL
# Write your MySQL query statement below
DELETE p1
FROM Person p1, Person p2
WHERE p1.Email = p2.Email AND
p1.Id > p2.Id
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Input
Output