ForeignKeyViolation

You get instances of ForeignKeyViolation from the Database methods foreignKeyViolations and foreignKeyViolations(in:in:) methods.

For example:

try dbQueue.read {
    let violations = try db.foreignKeyViolations()
    while let violation = try violations.next() {
        // The name of the table that contains the `REFERENCES` clause
        violation.originTable

        // The rowid of the row that contains the invalid `REFERENCES` clause, or
        // nil if the origin table is a `WITHOUT ROWID` table.
        violation.originRowID

        // The name of the table that is referred to.
        violation.destinationTable

        // The id of the specific foreign key constraint that failed. This id
        // matches `ForeignKeyInfo.id`. See `Database.foreignKeys(on:)` for more
        // information.
        violation.foreignKeyId

        // Plain description:
        // "FOREIGN KEY constraint violation - from player to team, in rowid 1"
        String(describing: violation)

        // Rich description:
        // "FOREIGN KEY constraint violation - from player(teamId) to team(id),
        //  in [id:1 teamId:2 name:"O'Brien" score:1000]"
        try violation.failureDescription(db)

        // Turn violation into a DatabaseError
        throw violation.databaseError(db)
    }
}

Related SQLite documentation: https://www.sqlite.org/pragma.html#pragma_foreign_key_check