180607_del_duplicate
2018-06-07 本文已影响0人
郑磊_4135
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 | |
|---|---|
| 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 | |
|---|---|
| 1 | john@example.com |
| 2 | bob@example.com |
DELETE P2
FROM Person P1, Person P2
WHERE P1.Email = P2.Email
AND P1.Id < P2.Id
