MySQL 是否会在更新时覆盖相同值的列?
在 MySQL 中更新表时，例如:
When updating a table in MySQL, for example:
表格 用户
user_id | user_name
1 John
2 Joseph
3 Juan
如果我运行查询
UPDATE `user` SET user_name = 'John' WHERE user_id = 1
MySQL 会再次写入相同的值还是忽略它，因为它是相同的内容?
Will MySQL write the same value again or ignore it since it's the same content?
推荐答案
作为 MySQL UPDATE 语句手册 暗示，
如果您将列设置为其当前具有的值，MySQL 会注意到这一点并且不更新它.
If you set a column to the value it currently has, MySQL notices this and does not update it.
因此，如果您运行此查询，MySQL 将了解您尝试应用的值与指定列的当前值相同，并且不会向数据库写入任何内容.
So, if you run this query, MySQL will understand that the value you're trying to apply is the same as the current one for the specified column, and it won't write anything to the database.
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