MySQL 外键错误。约束键错误

Question

我无法将外键添加到现有 table。报错如下

Executing:
ALTER TABLE `sms`.`student_account` 
ADD INDEX `student_id_idx` (`student_id` ASC) VISIBLE;
;
ALTER TABLE `sms`.`student_account` 
ADD CONSTRAINT `student_id`
  FOREIGN KEY (`student_id`)
  REFERENCES `sms`.`student` (`student_id`)
  ON DELETE RESTRICT
  ON UPDATE CASCADE;

ERROR 1064: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 2
SQL Statement:
ALTER TABLE `sms`.`student_account` 
ADD INDEX `student_id_idx` (`student_id` ASC) VISIBLE

Answer 1

我已经编写了以下可用的架构。我建议不要对已用于该列的约束使用相同的名称 student_id。我希望 fk_student_id 避免在某些时候出现歧义或冲突的风险。

create table `student_account` (
  student_id int);
create table  `student`(
  student_id int primary key
  );

✓

✓

ALTER TABLE `student_account` 
ADD INDEX `student_id_idx` (`student_id` ASC) VISIBLE;

✓

ALTER TABLE `student_account` 
ADD CONSTRAINT `student_id`
  FOREIGN KEY (`student_id`)
  REFERENCES `student` (`student_id`)
  ON DELETE RESTRICT
  ON UPDATE CASCADE;

✓

db<>fiddle here

MySQL 外键错误。约束键错误

MySQL Foreign Key ERROR. Constraint key error

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