[LeetCode][SQL]Delete Duplicate Emails
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时间：2015年06月12日
https://leetcode.com/problems/delete-duplicate-emails/
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 | [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 have the following rows:
+----+------------------+ | Id | Email | +----+------------------+ | 1 | [email protected] | | 2 | [email protected] | +----+------------------+
##need to link table ‘A.Email = B.Email‘ first !!!! delete A from Person A, Person B where A.Email = B.Email and A.Id > B.Id
delete语句里不能再select这个表，这种写法是过不了的。
delete A from Person A where A.Email in (select B.Email from Person B group by B.Email having count(*) > 1)
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