How to set cascade on SQLite database with compound primary foreign key?

问题

I have a db that's structured with a supertype table as well as subtype tables like so:

EVENT
PatientId INTEGER,
DateTime TEXT,
EventTypeCode TEXT,
PRIMARY KEY( PatientId, DateTime, EventTypeCode )

different types of events have their own tables and have the same primary key, except that it's foreign.

EXERCISE
PatientId INTEGER,
DateTime TEXT,
EventTypeCode TEXT,
PRIMARY KEY( PatientId, DateTime, EventTypeCode ) ON CONFLICT IGNORE,
CONSTRAINT "PrimaryKey" FOREIGN KEY ("PatientId", "EventTypeCode", "DateTime") REFERENCES "Event" ("PatientId", "EventTypeCode", "DateTime") ON DELETE CASCADE ON UPDATE CASCADE

When I try to delete an entry in Event, I get a foreign key mismatch and when I delete it in Exercise it deletes, but only in Exercise.. it does not cascade. What do I need to do to get the cascade to work properly? I would prefer to delete the entry in Event and have it cascade to Exercise.. which from the examples I've seen seems like how it should work...

回答1:

It is because you have set up an invalid foreign key. Even though SQLite allows you to set it up, it will error out when trying to enforce it.

http://www.sqlite.org/foreignkeys.html#fk_indexes

The parent key columns named in the foreign key constraint are not the primary key of the parent table and are not subject to a unique constraint using collating sequence specified in the CREATE TABLE

Foreign keys should be set up against a unique target. The column PatientId references Event(PatientID) is not valid, because PatientID alone in table Event is not unique.

EDIT

Foreign key support is only available on SQLite 3.6.19 or above. Depending on what tool you use, you also need to enable pragma foreign_keys explicitly. For SQLite Manager add-on for Firefox for example, see here http://code.google.com/p/sqlite-manager/wiki/ForeignKeys

This works for me
Caution!! don't drop your existing tables if they contain anything important. Try on a new db

drop table if exists event;
drop table if exists exercise;

create table EVENT (
PatientId INTEGER,
DateTime TEXT,
EventTypeCode TEXT,
PRIMARY KEY( PatientId, DateTime, EventTypeCode ));
create table EXERCISE(
PatientId INTEGER,
DateTime TEXT,
EventTypeCode TEXT,
PRIMARY KEY( PatientId, DateTime, EventTypeCode ) ON CONFLICT IGNORE,
CONSTRAINT "PrimaryKey" FOREIGN KEY ("PatientId", "EventTypeCode", "DateTime") REFERENCES "Event" ("PatientId", "EventTypeCode", "DateTime") ON DELETE CASCADE ON UPDATE CASCADE);
insert into Event (patientid, datetime, eventtypecode) values (1,2,3);
insert into Event (patientid, datetime, eventtypecode) values (4,5,6);
insert into Event (patientid, datetime, eventtypecode) values (7,9,8);
insert into Exercise (patientid, datetime, eventtypecode) values (1,2,3);
insert into Exercise (patientid, datetime, eventtypecode) values (7,9,8);

delete from event where patientid=1;

来源：https://stackoverflow.com/questions/5371371/how-to-set-cascade-on-sqlite-database-with-compound-primary-foreign-key

标签

sqlite

foreign-keys

relational-database

cascading-deletes

compound-key