Cascade Triggers in SQLite - database

Question

I've the following DB structure in SQLite:
I want to create a trigger that whenever I delete a country all the related districts, municipalities and parishes are also deleted (like MySQL InnoDB), I've tried using SQLite triggers and came up with this:
Districts:
CREATE TRIGGER [delete_country]
BEFORE DELETE
ON [countries]
FOR EACH ROW
BEGIN
DELETE FROM districts WHERE districts.id_countries = id;
END
Municipalities:
CREATE TRIGGER [delete_district]
BEFORE DELETE
ON [districts]
FOR EACH ROW
BEGIN
DELETE FROM municipalities WHERE municipalities.id_districts = id;
END
Parishes:
CREATE TRIGGER [delete_municipality]
BEFORE DELETE
ON [municipalities]
FOR EACH ROW
BEGIN
DELETE FROM parishes WHERE parishes.id_municipalities = id;
END
I haven't yet tested the delete_district and delete_municipality triggers because I get a strange behavior on the delete_country trigger: when I delete a country only the first related district gets deleted, all the others related districts remain in the table. What am I doing wrong?

Answer 1

The trigger looks like it is deleting districts whose id equals id_countries, that is, the where clause is actually
WHERE districts.id_countries = districts.id
You need to reference the id from the countries table. In a delete trigger, use "old" to do this.
CREATE TRIGGER [delete_country]
BEFORE DELETE
ON [countries]
FOR EACH ROW
BEGIN
DELETE FROM districts WHERE districts.id_countries = old.id;
END
Also, I would suggest changing your schema naming convention. Usually, the table name is singular, and corresponds to the entity in a row. I would have a country table with columns id and name, a district table with id, country_id and name, etc.
country
-------
id
name
district
-------
id
country_id
name
municipality
------------
id
district_id
name
parish
-----
id
municipality_id
name
Then the trigger would be
CREATE TRIGGER [delete_country]
BEFORE DELETE
ON [country]
FOR EACH ROW
BEGIN
DELETE FROM district WHERE district.country_id = old.id;
END

Answer 2

PRAGMA foreign_keys = 1;
This will enable the enforcement of foreign keys just like in MySQL. If you define your table with 'ON DELETE CASCADE' clause like so:
CREATE TABLE "notification" (
"rowid" INTEGER NOT NULL,
"user" INTEGER NOT NULL,
"task" TEXT NOT NULL,
"payload" TEXT NOT NULL,
PRIMARY KEY("rowid"),
FOREIGN KEY("user") REFERENCES "user" ON UPDATE CASCADE ON DELETE CASCADE
);
The whole row will be deleted when (in this case) it's parent user row is deleted.
P.S: I know this is a dead thread, but I figured I put this here for the people viewing in 2019. ;D