Manages a local database for weather data.

WeatherDbHelper.java

package com.example.android.sunshine.app.data;

//imports...

/** Manages a local database for weather data. */
public class WeatherDbHelper extends SQLiteOpenHelper {

    // If you change the database schema, you must increment the database version.
    private static final int DATABASE_VERSION = 2;

    static final String DATABASE_NAME = "weather.db";

    public WeatherDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase sqLiteDatabase) {
        final String SQL_CREATE_WEATHER_TABLE =
                "CREATE TABLE " + WeatherEntry.TABLE_NAME + " (" +
                WeatherEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                // the ID of the location entry associated with this weather data
                WeatherEntry.COLUMN_LOC_KEY + " INTEGER NOT NULL, " +
                WeatherEntry.COLUMN_DATE + " INTEGER NOT NULL, " +
                WeatherEntry.COLUMN_SHORT_DESC + " TEXT NOT NULL, " +
                WeatherEntry.COLUMN_WEATHER_ID + " INTEGER NOT NULL," +

                WeatherEntry.COLUMN_MIN_TEMP + " REAL NOT NULL, " +
                WeatherEntry.COLUMN_MAX_TEMP + " REAL NOT NULL, " +

                WeatherEntry.COLUMN_HUMIDITY + " REAL NOT NULL, " +
                WeatherEntry.COLUMN_PRESSURE + " REAL NOT NULL, " +
                WeatherEntry.COLUMN_WIND_SPEED + " REAL NOT NULL, " +
                WeatherEntry.COLUMN_DEGREES + " REAL NOT NULL, " +

                // Set up the location column as a foreign key to location table.
                " FOREIGN KEY (" + WeatherEntry.COLUMN_LOC_KEY + ") REFERENCES " +
                LocationEntry.TABLE_NAME + " (" + LocationEntry._ID + "), " +

                // To assure the application have just one weather entry per day
                // per location, it's created a UNIQUE constraint with REPLACE strategy
                " UNIQUE (" + WeatherEntry.COLUMN_DATE + ", " +
                WeatherEntry.COLUMN_LOC_KEY + ") ON CONFLICT REPLACE);";

        sqLiteDatabase.execSQL(SQL_CREATE_WEATHER_TABLE);

        final String SQL_CREATE_LOCATION_TABLE =
                "CREATE TABLE " + LocationEntry.TABLE_NAME + " (" +
                LocationEntry._ID + " INTEGER PRIMARY KEY, " +
                LocationEntry.COLUMN_LOCATION_SETTING + " TEXT UNIQUE NOT NULL, " +
                LocationEntry.COLUMN_CITY_NAME + " TEXT NOT NULL, " +
                LocationEntry.COLUMN_COORD_LAT + " REAL NOT NULL, " +
                LocationEntry.COLUMN_COORD_LONG + " REAL NOT NULL);";
        sqLiteDatabase.execSQL(SQL_CREATE_LOCATION_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + LocationEntry.TABLE_NAME);
        sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + WeatherEntry.TABLE_NAME);
        onCreate(sqLiteDatabase);
    }
}