Leetcode 182. Duplicate Emails

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182. Duplicate Emailsmy SubmissionsQuestionTotal accepted:14498 Total submissions:38364 difficulty:easy

Write a SQL query to the Find all duplicate emails in a table named Person .

+----+---------+| Id | Email   |+----+---------+| 1  | [Email protected] | | 2  | [Email protected] | | 3  | [Email protected] |+----+---------+

For example, your query should return the following for the above table:

+---------+| Email   |+---------+| [Email protected] |+---------+

Note:all emails is in lowercase.

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1 # Write Your MySQL query statement below 2 Select distinct  from 3       4         where p1. Email=5and              p1. Id!=P2. Id

About DISTINCT

SQL SELECT DISTINCT Statement

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This chapter explains the SELECT DISTINCT statement.

SQL SELECT DISTINCT Statement

In the table, duplicate values may be included. That's not a problem, but sometimes you might want to just list different values (distinct).

Keyword DISTINCT is used to return only different values.

Grammar:

SELECT DISTINCT column name from table name

Using DISTINCT Keywords

If you want to pick all the values from the company column, we need to use the SELECT statement:

SELECT Company from Orders

"Orders" table: Company

	OrderNumber
Ibm	3532
3wschool	2356
Apple	4698
3wschool	6953

Results:

Company
Ibm
3wschool
Apple
3wschool

Note that in the result set, 3wschool is listed two times.

To select only a different value from the company column, we need to use the Select DISTINCT statement:

DISTINCT

Results:

Company
Ibm
3wschool
Apple

Now, in the result set, "3wschool" is listed only once.

Leetcode 182. Duplicate Emails