mysql - 收到错误无法删除或更新父行 : a foreign key constraint fails even setting ON DELETE NO ACTION ON UPDATE NO ACTION

Question

我已经检查了所有与此错误有关的问题，但找不到我的答案

这是我的 EER 图 EER Diagram 我在 Sales 中插入一行，例如像这样(SellerFId=1，GoodFId=1，CustomerFId=1)所以我希望能够从他们自己的表中删除 Seller Or Good 或 Customer 这样在 Sales 中插入的行仍然保留我使用This Foreign Constrain between Sales and Other tables

 ON DELETE NO ACTION ON UPDATE NO ACTION

但是当我从他们自己的表中删除卖家或好人或客户时，mysql 不允许我并给我这个错误

Cannot delete or update a parent row: a foreign key constraint fails (newmobarakkabul.sales, CONSTRAINT fk_Sellers_has_Goods_has_Customers_Sellers1 FOREIGN KEY (SellerFId) REFERENCES staffs (StaffId) ON DELETE NO ACTION ON UPDATE NO ACTION)

具体来说，我的问题是，我是否真的需要在 Sales 表和其他表之间设置外键约束(如果不需要，那么这个查询“ON DELETE NO ACTION ON UPDATE NO ACTION”是什么？ )

Answer 1

在 MySQL 中，NO ACTION is an equivalent of RESTRICT

NO ACTION: A keyword from standard SQL. In MySQL, equivalent to RESTRICT. The MySQL Server rejects the delete or update operation for the parent table if there is a related foreign key value in the referenced table. Some database systems have deferred checks, and NO ACTION is a deferred check. In MySQL, foreign key constraints are checked immediately, so NO ACTION is the same as RESTRICT.

还有

RESTRICT: Rejects the delete or update operation for the parent table. Specifying RESTRICT (or NO ACTION) is the same as omitting the ON DELETE or ON UPDATE clause.

至于你最后一个问题，你是否真的需要这样的约束要根据你的应用程序的规范来确定。