SQLite - 如何在保留子/子行的同时删除父行？

Question

我了解PRAGMA foreign_key 和ON DELETE RESTRICT/NO ACTION 的概念，但我面临着另一种情况。

我需要删除父行但保持子行与其关联。例如：

CREATE TABLE A(id, name);
INSERT INTO A(id, name) VALUES (1, "Loreum");

CREATE TABLE B(id, id_A, name) FOREIGN KEY(id_A) REFERENCES A(id);
INSERT INTO B(id, id_A, name) VALUES (1, 1, "Opium");
DELETE FROM A WHERE id = 1;

我想实现这一点同时保持子行完整。这可能吗？

编辑

上面的示例将我的问题与this question 分开。示例可能会帮助某些人，他们只有在有代码时才能理解。

Answer 1

您可以使用deferred foreign key constraint：

PRAGMA foreign_keys = on;
CREATE TABLE A(id PRIMARY KEY, name);
INSERT INTO A(id, name) VALUES (1, "Loreum");
CREATE TABLE B(id, id_A, name, FOREIGN KEY(id_A) REFERENCES A(id) DEFERRABLE INITIALLY DEFERRED);
INSERT INTO B(id, id_A, name) VALUES (1, 1, "Opium");

BEGIN;
DELETE FROM A WHERE id = 1;
INSERT INTO A(id, name) VALUES (1, "another Loreum");
COMMIT;