BDs

Bases de datos

• Información guardada en tablas

• Columnas, instancias de objetos ->filas

• SQL 

• SQLite Database 

• .query(args) 

• .rawQuery(consulta SQL, null)

SQL

//Crear: 

CREATE TABLE intents (id INTEGER PRIMARY KEY AUTOINCREMENT, user TEXT, number INTEGER) 

//Seleccionar: 

SELECT id _id, user, number FROM intents ORDER BY number DESC 

//Insertar: 

INSERT INTO intents (user, number) VALUES (’usuario1’, ‘5’) 

//Eliminar: 

DELETE FROM intents WHERE user=’user1’

SQLite Open Helper

public class IntentsOpenHelper extends SQLiteOpenHelper { 

    private static final int DATABASE_VERSION = 1; 

    private static final String DATABASE_NAME = "project"; 

    private static final String STATISTICS_TABLE_NAME = "intents"; 

    private static final String STATISTICS_TABLE_CREATE = 
        "CREATE TABLE " + STATISTICS_TABLE_NAME + 
        " (id INTEGER PRIMARY KEY AUTOINCREMENT, user TEXT, number INTEGER)"; 

    IntentsOpenHelper(Context context) { 
        super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    } 
    
    @Override 
    public void onCreate(SQLiteDatabase db) { 
        db.execSQL(STATISTICS_TABLE_CREATE); 
    } 
    
    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
        db.execSQL("DROP TABLE IF EXISTS " + STATISTICS_TABLE_NAME); 
        db.execSQL(STATISTICS_TABLE_CREATE); 
    } 
}

Uso del Open Helper

IntentsOpenHelper ioh = new IntentsOpenHelper(this); 

SQLiteDatabase db = ioh.getReadableDatabase(); 

SQLiteDatabase db = ioh.getWritableDatabase(); 

if (db != null) { 

 db.execSQL("INSERT INTO ...", null); 
 db.execSQL("DELETE FROM ...", null); 
 cursor = db.rawQuery("SELECT id ...", null); 
 db.close(); 
}