将外键约束设置为0并不是一个好主意，因为如果这样做，数据库将不能确保它没有违反引用完整性。这可能导致不准确、误导或不完整的数据。

使用外键是有原因的:因为子列中的所有值都应该与父列中的值相同。如果没有外键约束，子行可以有不在父行中的值，这将导致不准确的数据。

For instance, let's say you have a website for students to login and every student must register for an account as a user. You have one table for user ids, with user id as a primary key; and another table for student accounts, with student id as a column. Since every student must have a user id, it would make sense to make the student id from the student accounts table a foreign key that references the primary key user id in the user ids table. If there are no foreign key checks, a student could end up having a student id and no user id, which means a student can get an account without being a user, which is wrong.

想象一下，如果它发生在大量数据上。这就是为什么你需要外键检查。

最好弄清楚是什么导致了错误。最有可能的情况是，您试图从父行删除而不删除子行。尝试先从子行删除，再从父行删除。

如果键字段是可空的，那么你也可以在尝试删除它之前将值设置为空:

cursor.execute("UPDATE myapp_item SET myapp_style_id = NULL WHERE n = %s", n)
transaction.commit_unless_managed() 

cursor.execute("UPDATE myapp_style SET myapp_item_id = NULL WHERE n = %s", n)
transaction.commit_unless_managed()

cursor.execute("DELETE FROM myapp_item WHERE n = %s", n)
transaction.commit_unless_managed()

cursor.execute("DELETE FROM myapp_style WHERE n = %s", n)
transaction.commit_unless_managed()

要在全局范围内关闭外键约束，请执行以下操作:

SET GLOBAL FOREIGN_KEY_CHECKS=0;

完成后记得把它调回去

SET GLOBAL FOREIGN_KEY_CHECKS=1;

警告:只有在进行单用户模式维护时才应该这样做。因为这可能会导致数据不一致。例如，当您使用mysqldump输出上传大量数据时，它将非常有用。

将外键约束设置为0并不是一个好主意，因为如果这样做，数据库将不能确保它没有违反引用完整性。这可能导致不准确、误导或不完整的数据。

使用外键是有原因的:因为子列中的所有值都应该与父列中的值相同。如果没有外键约束，子行可以有不在父行中的值，这将导致不准确的数据。

For instance, let's say you have a website for students to login and every student must register for an account as a user. You have one table for user ids, with user id as a primary key; and another table for student accounts, with student id as a column. Since every student must have a user id, it would make sense to make the student id from the student accounts table a foreign key that references the primary key user id in the user ids table. If there are no foreign key checks, a student could end up having a student id and no user id, which means a student can get an account without being a user, which is wrong.

想象一下，如果它发生在大量数据上。这就是为什么你需要外键检查。

最好弄清楚是什么导致了错误。最有可能的情况是，您试图从父行删除而不删除子行。尝试先从子行删除，再从父行删除。

phpMyAdmin的一个非常简单的解决方案:

在您的表中，转到SQL选项卡 在编辑要运行的SQL命令后，在GO旁边有一个复选框，名为“启用外键检查”。 取消选中此复选框并运行SQL。执行后将自动重新检查。

尝试禁用键或

SET FOREIGN_KEY_CHECKS=0;

一定要

SET FOREIGN_KEY_CHECKS=1;

后。