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Android transaction or trigger?

开发者 https://www.devze.com 2023-02-21 06:22 出处:网络
I am working on a fuel use application which will run on Android 1.6 onwards. The bundled SQLite on v1.6 doesn\'t do foreign keys, so I\'ve had to handle it manually. So far, I have done this using an

I am working on a fuel use application which will run on Android 1.6 onwards. The bundled SQLite on v1.6 doesn't do foreign keys, so I've had to handle it manually. So far, I have done this using an Android transaction:

    public static long addFuelUp(String registrationNumber, String date)
{
    SQLiteDatabase db = uKMpgData.getReadableDatabase();
    lon开发者_JS百科g result = -1;
    ContentValues values = new ContentValues();
    Cursor vehicleCursor = VehicleDataProvider.getVehicle(registrationNumber);

    if(vehicleCursor.moveToNext())
    {
        Cursor fuelUpsCursor = getFuelUps(registrationNumber, date);
        if(!fuelUpsCursor.moveToNext())
        {
            db.beginTransaction();
            try
            {
                    values.put(REGISTRATION_NO_COLUMN, registrationNumber.replace(" ", ""));
                    values.put(DATE_TIME_COLUMN, date);
                    result = db.insertOrThrow(FUEL_USE_TABLE_NAME, null, values);
                    db.setTransactionSuccessful();
            }
            catch(SQLException e)
            {
                Log.d("addFuelUp", e.getMessage());
            }
            finally
            {
                db.endTransaction();
                vehicleCursor.close();
                fuelUpsCursor.close();
            }
        }
    }
    return result;
}

I.e. fuel data cannot be entered unless there is a matching vehicle registration number in the database.

My question is, is there a better way to do this? I'm not a database expert, but I know you can set up triggers to enforce rules - are triggers more suited to handle constraints?

Cheers, Barry


Triggers would be a good solution to this problem.

In fact there is an automated way to generate triggers for simulating foreign keys. SQLite for PC provides a utility called "genfkey" which can examine an existing database which uses foreign keys and outputs the corresponding triggers.

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