Sql-delete Duplicate Emails

Source: Internet
Author: User

Write a SQL query to delete all duplicate e-mail entries in a table named Person , keeping 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 has the following rows:

+----+------------------+| Id | Email            |+----+------------------+| 1  | [Email protected] | | 2  | [email protected]  | +----+------------------+
Ideas:
(1) First say inner join (equivalent to join), and his derivative left/right join. Their essence is to add additional conditions on the basis of the Cartesian product.
(2) then the delete format:
Delete from table where:
Delete from p1using person P1 inner join person p2on p1. Id > P2. Id and P1. Email = P2. Email

Sql-delete Duplicate Emails

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