MySQL: ON UPDATE SET DEFAULT 似乎不应该引发错误

Question

我有这个代码：

CREATE TABLE CarDrivers (
  driver_name VARCHAR (50) UNIQUE
);

INSERT INTO CarDrivers (driver_name) VALUES ("John"), ("Jarvis");

CREATE TABLE Cars (
  driver_name VARCHAR (50) DEFAULT "John",
  -- driver_names are connected
  FOREIGN KEY (driver_name) REFERENCES CarDrivers (driver_name)
  -- but we can always return to value "John", which is present in CarDrivers
  ON UPDATE SET DEFAULT
);

INSERT INTO Cars SET driver_name = 'Jarvis';

-- this is where the error happens
UPDATE CarDrivers SET driver_name = 'Jarvease' WHERE driver_name = 'Jarvis';

代码导致错误：

Cannot delete or update a parent row. A foreign key constraint fails: ....Cars, CONSTRAINT Cars_ibfk_1 FOREIGN KEY (driver_name) REFERENCES CarDrivers (driver_name)

当我们告诉 Cars table CarDrivers.driver_name Cars.driver_name 的 ON UPDATE 应该设置为 [=22 时，为什么会出现此错误=]，这是一个值 CarDrivers.driver_name?

顺便说一句，约束 ... ON UPDATE SET NULL ... ON UPDATE CASCADE 正常工作并允许我们更新 CarDrivers.driver_name!

感谢您的宝贵时间！

Answer 1

https://dev.mysql.com/doc/refman/8.0/en/create-table-foreign-keys.html 说：

SET DEFAULT: This action is recognized by the MySQL parser, but both InnoDB and NDB reject table definitions containing ON DELETE SET DEFAULT or ON UPDATE SET DEFAULT clauses.

换句话说，这个功能在MySQL的当前版本中不起作用。

MySQL: ON UPDATE SET DEFAULT 似乎不应该引发错误

MySQL: ON UPDATE SET DEFAULT raises an error when it seems like it shouldn't

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foreign-keys