SQLite

Question

我理解 PRAGMA foreign_key 和 ON DELETE RESTRICT/NO ACTION 的概念，但我面临的情况不同。

我需要删除父行但保留与其相关联的子行。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;

我想实现这个同时保持子行完整。这可能吗？

编辑

上面的示例将我的问题与 this question 区分开来。示例可能会帮助一些只有在有代码时才能理解的人。

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;

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foreign-keys