196. 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 | 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 |
+----+------------------+ 删除重复的地址,保留ID最小的 MySQL(714ms):
DELETE FROM Person
WHERE Id NOT IN (
SELECT * FROM(
SELECT MIN(Id)
FROM Person
GROUP BY Email
) AS Mid
);
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