标签:charset not weight var utf8 span create inf value
CREATE TABLE `user1_test` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_name` varchar(20) DEFAULT NULL, `over` varchar(20) DEFAULT NULL, `mobile` varchar(200) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `user1_test` VALUES (‘1‘, ‘唐僧‘, ‘qujing‘, ‘12345678901,12345678902,12345678903‘); INSERT INTO `user1_test` VALUES (‘2‘, ‘猪八戒‘, ‘qujing‘, ‘22345678901,22345678902,22345678903‘); INSERT INTO `user1_test` VALUES (‘3‘, ‘孙悟空‘, ‘qujing‘, ‘32345678901,32345678902‘); INSERT INTO `user1_test` VALUES (‘4‘, ‘沙僧‘, ‘qujing‘, ‘42345678901‘); INSERT INTO `user1_test` VALUES (‘8‘, ‘唐僧‘, ‘qujing‘, ‘12345678901,12345678902,12345678903‘); INSERT INTO `user1_test` VALUES (‘9‘, ‘猪八戒‘, ‘qujing‘, ‘22345678901,22345678902,22345678903‘);
MySQL-利用主键删除重复数据
1.查询数据是否重复
SELECT user_name,COUNT(*) FROM user1_test GROUP BY user_name HAVING COUNT(*)>1;
2.删除重复数据,对于相同数据保留ID最大的
SELECT a.*,b.* FROM user1_test a JOIN( SELECT user_name,COUNT(*),MAX(id) AS id FROM user1_test GROUP BY user_name HAVING COUNT(*)>1) b ON a.user_name=b.user_name WHERE a.id<b.id;
DELETE a FROM user1_test a JOIN( SELECT user_name,COUNT(*),MAX(id) AS id FROM user1_test GROUP BY user_name HAVING COUNT(*)>1) b ON a.user_name=b.user_name WHERE a.id<b.id;
标签:charset not weight var utf8 span create inf value
原文地址:https://www.cnblogs.com/ooo0/p/12252739.html