How to create a foreign key in swift sqlite3? - ios

Question

I am trying to create a sqlite table containing a foreign key, using the default sqlite3 library from swift/xCode via import sqlite3. The table is getting created without the key, but if I add the foreign key to the statement, I get a syntax error.
Error: [logging] near "date": syntax error
"""
CREATE TABLE IF NOT EXISTS measurement(
measurementid INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
accountid INTEGER NOT NULL,
FOREIGN KEY(accountid) REFERENCES accounts(userid),
date TEXT NOT NULL,
measurementtype TEXT NOT NULL,
moodmeasurementid INTEGER,
healthmeasurementid INTEGER,
bodymeasurementid INTEGER,
workout TEXT NOT NULL
);
"""
"""
CREATE TABLE IF NOT EXISTS accounts(
userid INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
email TEXT NOT NULL,
password TEXT NOT NULL,
firstname TEXT NOT NULL,
lastname TEXT NOT NULL,
birthday TEXT NOT NULL,
gender TEXT NOT NULL,
creationdate TEXT NOT NULL
);
"""
After some research I read, that you might need to activate foreign keys, before using them. So I added the following code, but I still get the same error.
if sqlite3_exec(dbPointer, "PRAGMA foreign_keys = ON", nil, nil, nil) != SQLITE_OK {
let err = String(cString: sqlite3_errmsg(dbPointer))
print("error attempting to enable foreign keys: \(err)")
}
Also adding it to the end of the statement didn't fix it.

Answer 1

You are using the table constraint syntax instead of the column constraint syntax.
You want:
accountid INTEGER NOT NULL
REFERENCES accounts(userid),
The FOREIGN KEY(accountid) would be needed if you were adding the constraint to the table. Also note the removal of the comma after NOT NULL.
See https://www.sqlite.org/lang_createtable.html for complete details of the syntax.