如何在Mysql中处理外键约束失败

Question

当我尝试将数据添加到children表时。

我犯了以下错误。

我试着找出原因。。

插入数据是否有任何错误之处？

如果有人有意见，请告诉我

感谢

QueryFailedError: ER_NO_REFERENCED_ROW_2: Cannot add or update a child row: a foreign key constraint fails (`mogucare_db`.`children`, CONSTRAINT `FK_644df4cc525729181dbee86a44d` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION)

以下是我对DB的看法。

mysql> select * from children;
Empty set (0.00 sec)
mysql> select * from users;
Empty set (0.00 sec)

mysql> desc children;
+--------------+--------------+------+-----+----------------------+----------------+
| Field        | Type         | Null | Key | Default              | Extra          |
+--------------+--------------+------+-----+----------------------+----------------+
| id           | int(11)      | NO   | PRI | NULL                 | auto_increment |
| user_id      | int(11)      | NO   | MUL | NULL                 |                |
| mogu_plus_id | varchar(255) | NO   |     | NULL                 |                |
| first_name   | varchar(255) | NO   |     | NULL                 |                |
| middle_name  | varchar(255) | YES  |     | NULL                 |                |
| last_name    | varchar(255) | NO   |     | NULL                 |                |
| birthday     | date         | NO   |     | NULL                 |                |
| gender       | varchar(255) | NO   |     | NULL                 |                |
| blood_type   | varchar(255) | NO   |     | NULL                 |                |
| class        | varchar(255) | YES  |     | NULL                 |                |
| entrance_day | varchar(255) | YES  |     | NULL                 |                |
| is_active    | int(11)      | NO   |     | NULL                 |                |
| created_at   | datetime(6)  | NO   |     | CURRENT_TIMESTAMP(6) |                |
| updated_at   | datetime(6)  | NO   |     | CURRENT_TIMESTAMP(6) |                |
| deleted_at   | datetime(6)  | YES  |     | NULL                 |                |
+--------------+--------------+------+-----+----------------------+----------------+
15 rows in set (0.01 sec)

mysql> desc users;
+-------------------+--------------+------+-----+----------------------+----------------+
| Field             | Type         | Null | Key | Default              | Extra          |
+-------------------+--------------+------+-----+----------------------+----------------+
| id                | int(11)      | NO   | PRI | NULL                 | auto_increment |
| password          | varchar(255) | NO   |     | NULL                 |                |
| birthday          | date         | NO   |     | NULL                 |                |
| address           | varchar(255) | NO   |     | NULL                 |                |
| email             | varchar(255) | NO   |     | NULL                 |                |
| gender            | varchar(255) | NO   |     | NULL                 |                |
| height            | varchar(255) | NO   |     | NULL                 |                |
| weight            | varchar(255) | NO   |     | NULL                 |                |
| phone             | varchar(255) | NO   |     | NULL                 |                |
| login_id          | varchar(255) | NO   |     | NULL                 |                |
| first_name        | varchar(255) | NO   |     | NULL                 |                |
| middle_name       | varchar(255) | YES  |     | NULL                 |                |
| last_name         | varchar(255) | NO   |     | NULL                 |                |
| blood_type        | varchar(255) | NO   |     | NULL                 |                |
| language_cd       | int(11)      | NO   |     | NULL                 |                |
| emergency_contact | varchar(255) | YES  |     | NULL                 |                |
| is_admin          | int(11)      | NO   |     | NULL                 |                |
| created_at        | datetime(6)  | NO   |     | CURRENT_TIMESTAMP(6) |                |
| updated_at        | datetime(6)  | NO   |     | CURRENT_TIMESTAMP(6) |                |
| deleted_at        | datetime(6)  | YES  |     | NULL                 |                |
+-------------------+--------------+------+-----+----------------------+----------------+
20 rows in set (0.00 sec)

Answer 1

查看您的错误，在我看来，表Children在字段User_Id上有一个外键，该外键需要与表Users中现有的Id相匹配

因此，一切都正常工作，如果没有对表Users中的行的有效引用，就不能在表Children的行中输入。

因此，首先在表Users中创建一行或多行，然后可以在表Children创建一行，该行引用表Users中的一行