标签:196 example Person Duplicate id table Id com LeetCode
196. Delete Duplicate Emails
Easy
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 | | 3 | john@example.com | +----+------------------+ 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 | john@example.com | | 2 | bob@example.com | +----+------------------+
Note:
Your output is the whole Person
table after executing your sql. Use delete
statement.
代码
delete from Person where id not in(
select t.id from (
select min(id) as id from Person group by email
) t
)
评论
MySQL不允许DELETE的WHERE从句中查询被DELETE的表,但是可以通过嵌套一层SELECT的方式规避这个问题
标签:196,example,Person,Duplicate,id,table,Id,com,LeetCode 来源: https://blog.csdn.net/da_kao_la/article/details/99696380
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