Done S07.03-ConflictResolutionPolicy

S07.03-Exercise-ConflictResolutionPolicy/app/src/main/java/com/example/android/sunshine/data/WeatherDbHelper.java

@@ -44,7 +44,7 @@ public class WeatherDbHelper extends SQLiteOpenHelper {
      * use-case, we wanted to watch out for it and warn you what could happen if you mistakenly
      * version your databases.
      */
-    private static final int DATABASE_VERSION = 2;
+    private static final int DATABASE_VERSION = 3;
 
     public WeatherDbHelper(Context context) {
         super(context, DATABASE_NAME, null, DATABASE_VERSION);
@@ -85,9 +85,16 @@ public void onCreate(SQLiteDatabase sqLiteDatabase) {
                 WeatherEntry.COLUMN_PRESSURE   + " REAL NOT NULL, "                    +
 
                 WeatherEntry.COLUMN_WIND_SPEED + " REAL NOT NULL, "                    +
-                WeatherEntry.COLUMN_DEGREES    + " REAL NOT NULL" + ");";
+                WeatherEntry.COLUMN_DEGREES    + " REAL NOT NULL, "                    +
 
 //              TODO (1) Add a UNIQUE constraint on the date column to replace on conflict
+                /*
+                 * To ensure this table can only contain one weather entry per date, we declare
+                 * the date column to be unique. We also specify "ON CONFLICT REPLACE". This tells
+                 * SQLite that if we have a weather entry for a certain date and we attempt to
+                 * insert another weather entry with that date, we replace the old weather entry.
+                 */
+                " UNIQUE (" + WeatherEntry.COLUMN_DATE + ") ON CONFLICT REPLACE);";
 
         /*
          * After we've spelled out our SQLite table creation statement above, we actually execute