級聯觸發器SQLite中

Question

我有以下DB結構的SQLite：

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

我想創建一個觸發器，每當我刪除一個國家的所有相關區，市和教區也被刪除（像MySQL的InnoDB），我使用SQLite觸發器，並試圖用此想出了：

地區：

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

個

直轄市：

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

教區：

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

我還沒有測試的delete_district和delete_municipality觸發，因爲我上delete_country觸發一個奇怪的現象：當我刪除國家只有第一個相關區被刪除，所有其他相關區都留在表中。我究竟做錯了什麼？

Answer 1

觸發看起來是刪除其地區ID等於id_countries，也就是在where子句實際上是

WHERE districts.id_countries = districts.id 

您需要從國家表引用的ID。在刪除觸發器中，使用「old」來執行此操作。

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

此外，我會建議更改您的架構命名約定。通常，表名是單數的，並且對應於一行中的實體。我將同列編號和名稱，用ID，COUNTRY_ID和名稱的分區表等國表

country 
------- 
id 
name 

district 
------- 
id 
country_id 
name 

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

parish 
----- 
id 
municipality_id 
name 

則觸發將

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