QUERY 同样可以使用索引, 查询结果的status值为“cancelled_by_driver”
SELECT * FROM Trips WHERE status=2;
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第十二题
Delete Duplicate Emails
Write a SQL query to delete all duplicate email entries in a table namedPerson, keeping only unique emails based on its smallest Id.
建表及插入测试数据
drop table person purge;create table person(id int,email char(50));insert into person(id,email) values(1,'jo@ex.com');insert into person(id,email) values(2,'jo@ex.com');insert into person(id,email) values(3,'jo@ex.com'); |
mysql 版本-1
DELETE p1 FROM Person p1 INNER JOIN Person p2 WHERE p1.Email = p2.Email AND p1.Id > p2.Id; |
mysql 版本-2
DELETE FROM p1 USING Person p1 INNER JOIN Person p2 WHERE p1.Email = p2.Email AND p1.Id > p2.Id; |
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Sugeei