I'm using Ruby with SQLite3 and my attempts to use foreign keys in Sqlite3 were unfortunately not successful. According to sqlite3 --version
, version 3.7.13 is installed. As far as I know, Sqlite3 supports foreign keys since version 3.6.x.
I know that foreign keys are deactivated by default and have to be activated with PRAGMA foreign_keys = ON;
. In my Ruby db-create-script, I'm doing something like this:
sql = <<-SQL
PRAGMA foreign_keys = ON;
CREATE TABLE apps (
id ....
);
CREATE TABLE requests (
...
app_id INTEGER NOT NULL,
FOREIGN KEY(app_id) REFERENCES apps(id),
);
...
SQL
db.execute_batch(sql)
Unfortunately, I can happily insert rows into requests
with unknown app-ids, it works, but of course it shouldn't.
Interesting: using the sqlite3 shell directly, I can observe the following behaviour:
$ sqlite3 database.db
sqlite> PRAGMA foreign_keys = ON;
sqlite> PRAGMA foreign_keys;
1 // as expected
sqlite> .quit
$ sqlite3 database.db
sqlite> PRAGMA foreign_keys;
0 // off ?!
Without quitting the sqlite3 shell, foreign keys are working after activating them (and not quitting the shell) and I'm not allowed to insert rows with unknown app_ids.
I think I can answer my own question: The documentation says: Foreign key constraints are disabled by default (for backwards compatibility), so must be enabled for each database connection separately . Annoying, but it's finally working now.
Put this at the top of the file that executes the SQL commands and it will enable foreign keys on runtime.
db = SQLite3::Database.new("database.db")
db.execute("PRAGMA foreign_keys = ON")
One way of permanently turning on foreign_keys by default is to inject the following line into ~/.sqliterc
:
PRAGMA foreign_keys = ON;
Please note that it will affect all your databases...
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