级联触发器SQLite中

Question

我有以下DB结构的SQLite：

db structure http://i39.tinypic.com/kb3qef.jpg

我想创建一个触发器，每当我删除一个国家的所有相关区，市和教区也被删除（像MySQL的InnoDB），我使用SQLite触发器，并试图用此想出了：

地区：

CREATE TRIGGER [delete_country] 
BEFORE DELETE 
ON [countries] 
FOR EACH ROW 
BEGIN 
DELETE FROM districts WHERE districts.id_countries = id; 
END 

个

直辖市：

CREATE TRIGGER [delete_district] 
BEFORE DELETE 
ON [districts] 
FOR EACH ROW 
BEGIN 
DELETE FROM municipalities WHERE municipalities.id_districts = id; 
END 

教区：

CREATE TRIGGER [delete_municipality] 
BEFORE DELETE 
ON [municipalities] 
FOR EACH ROW 
BEGIN 
DELETE FROM parishes WHERE parishes.id_municipalities = id; 
END 

我还没有测试的delete_district和delete_municipality触发，因为我上delete_country触发一个奇怪的现象：当我删除国家只有第一个相关区被删除，所有其他相关区都留在表中。我究竟做错了什么？

Answer 1

触发看起来是删除其地区ID等于id_countries，也就是在where子句实际上是

WHERE districts.id_countries = districts.id 

您需要从国家表引用的ID。在删除触发器中，使用“old”来执行此操作。

CREATE TRIGGER [delete_country] 
BEFORE DELETE 
ON [countries] 
FOR EACH ROW 
BEGIN 
DELETE FROM districts WHERE districts.id_countries = old.id; 
END 

此外，我会建议更改您的架构命名约定。通常，表名是单数的，并且对应于一行中的实体。我将同列编号和名称，用ID，COUNTRY_ID和名称的分区表等国表

country 
------- 
id 
name 

district 
------- 
id 
country_id 
name 

municipality 
------------ 
id 
district_id 
name 

parish 
----- 
id 
municipality_id 
name 

则触发将

CREATE TRIGGER [delete_country] 
BEFORE DELETE 
ON [country] 
FOR EACH ROW 
BEGIN 
DELETE FROM district WHERE district.country_id = old.id; 
END