Mysql Duplicate entry ‘xxx‘ for key ‘xxx‘

Preface ： Recording errors , Pretty good , generous with your criticism

There's a picture, there's a truth

1、 problem ：

         Pictured parent_id and sku_id It's the only index , The query prompts that the unique index is duplicate ！

2、 doubt ：

         Is it really repeated ？mysql Whether to set case sensitivity ？

3、 analysis ：

         As shown in the figure, user defined skuId,ZC05、zc05 Is different , The problem is mysql Is case insensitive , Lead to repetition !

4、 solve ：

         You need to set the case sensitivity

        MySQL The character order names in follow the naming convention ： Starts with the name of the character set corresponding to the character order ;

         With _ci( Indicates case insensitive )、_cs( Indicates case sensitivity ) or _bin( Compare by code value ) ending .

5、 test :

        situation 1、 Create table statement

CREATE TABLE `test_user` (
  `user_id` int NOT NULL AUTO_INCREMENT,
  `user_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
  `password` int DEFAULT NULL,
  `email` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `sex` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `invalid` int DEFAULT NULL,
  `createTime` datetime DEFAULT NULL,
  `updateTime` datetime DEFAULT NULL,
  PRIMARY KEY (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

 

If you need to be case sensitive , Then the query is wrong

2、 Modify sort set , The query is normal

  `user_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_as_cs DEFAULT NULL,

 

3、 Modify sort set , It's normal

  `user_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,