MySQL 去重

本文主要是介绍MySQL 去重，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

• 方式一

DELETE FROM t_test 
WHERE id IN 
(SELECT * FROM
 (SELECT MAX(id) did FROM t_test GROUP BY username HAVING COUNT(*) > 1) t);

• 方式二

DELETE FROM t_test 
WHERE id NOT IN 
(SELECT t.minno FROM 
 (SELECT MIN(id) AS minno FROM t_test GROUP BY username) t);

执行效率一优于二

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