Question

I’m developping an Sms Application,
I’m trying to get the last sms from each conversation.

here’s my SQL Statement :

SELECT MAX(smsTIMESTAMP) AS smsTIMESTAMP,_id, smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTYPE, smsSHORTMSG, COUNT(*) AS smsNUMMESSAGES FROM sms GROUP BY smsCONID ORDER BY smsTIMESTAMP desc

I ran the query in SQLite Expert and I get the right response :

however when I run it in my app I get :

Here’s my table

Here’s My Datamanipulator Class :

public class DataManipulator {
    private static final  String DATABASE_NAME = "smsapplication.db";
    private static final int DATABASE_VERSION = 3;
    static final String TABLE_NAME = "sms";
    private static Context context;
    static SQLiteDatabase db;
    private static DataManipulator instance;

    private SQLiteStatement insertStmt;

    private static final String INSERT = "insert or ignore into "
        + TABLE_NAME + " (smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTIMESTAMP, smsTYPE, smsSHORTMSG) values (?,?,?,?,?,?,?,?)";

    public DataManipulator(Context context) {
        DataManipulator.context = context;
        OpenHelper openHelper = new OpenHelper(DataManipulator.context);
        DataManipulator.db = openHelper.getWritableDatabase();
        this.insertStmt = DataManipulator.db.compileStatement(INSERT);
    }
    public static DataManipulator getInstance(Context mContext)
    {
        if(instance == null)
        {
            instance = new DataManipulator(mContext);
        }
        return instance;
    }
    public long insert(int smsID, int smsCONID, String smsMSG,
            String smsNUM, int smsREAD, long smsTIMESTAMP, String smsTYPE, String smsSHORTMSG) {
        this.insertStmt.bindLong(1, smsID);
        this.insertStmt.bindLong(2, smsCONID);
        this.insertStmt.bindString(3, smsMSG);
        this.insertStmt.bindString(4, smsNUM);
        this.insertStmt.bindLong(5, smsREAD);
        this.insertStmt.bindString(6, String.valueOf(smsTIMESTAMP));
        this.insertStmt.bindString(7, smsTYPE);
        this.insertStmt.bindString(8, smsSHORTMSG);
        return this.insertStmt.executeInsert();
    }

    public void deleteAll() {
        db.delete(TABLE_NAME, null, null);
    }

    public Cursor getLastSmsForAllConversations()
    {
        Cursor cursor = db.query(TABLE_NAME, new String[] {"_id"," MAX(smsTIMESTAMP) AS smsTIMESTAMP ", "smsCONID", "smsNUM", "smsREAD", "smsTYPE","smsSHORTMSG","COUNT(*) AS smsNUMMESSAGES"  },
                null, null, "smsCONID", null, "smsTIMESTAMP desc"); 
        return cursor;
    }
    public Cursor getConversationMessages(int conID)
    {
        Cursor cursor = db.query(TABLE_NAME, new String[] {"_id", "smsID", "smsCONID", "smsMSG", "smsNUM", "smsREAD", "smsTIMESTAMP", "smsTYPE","smsSHORTMSG"  },
                "smsCONID="+conID, null, null, null, "smsTIMESTAMP asc"); 
        return cursor;
    }
    public void printCursor()
    {
        Cursor cursor = db.rawQuery("SELECT MAX(smsTIMESTAMP) AS smsTIMESTAMP,_id, smsID, smsCONID, smsMSG, smsNUM, smsREAD, smsTYPE, smsSHORTMSG, COUNT(*) AS smsNUMMESSAGES FROM sms GROUP BY smsCONID ORDER BY smsTIMESTAMP desc", null);

            //  db.query(TABLE_NAME, new String[] {"_id","smsTIMESTAMP AS smsTIMESTAMP ", "smsCONID", "smsNUM", "smsREAD", "smsTYPE","smsSHORTMSG"  },"smsCONID=40", null, null, null, "smsTIMESTAMP desc");  
        if (cursor.moveToFirst()){
               do{
                  String data ="";
                  data= cursor.getString(cursor.getColumnIndex("smsTIMESTAMP"))+" - " +cursor.getString(cursor.getColumnIndex("smsSHORTMSG"));
                  Log.i("data", data);
               }while(cursor.moveToNext()); 
            }
            cursor.close();
    }

    private static class OpenHelper extends SQLiteOpenHelper {

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

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL("CREATE TABLE " + TABLE_NAME + " (_id INTEGER , smsID INTEGER PRIMARY KEY, smsCONID INTEGER, smsMSG TEXT,smsNUM TEXT, smsREAD INTEGER, smsTIMESTAMP INTEGER, smsTYPE TEXT, smsSHORTMSG TEXT)");
        }

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

            if (db != null)
                db.close();

            super.close();

            }
    } 
}

Answer 1

When you are using GROUP BY, each row of the result corresponds to multiple rows of the original table.
There are three possibilities how these results are computed:

• Columns with an aggregate function like MAX or COUNT compute the values from all rows in the group;
• columns that appear in the GROUP BY clause are just taken from any record in the group (because all records in the group have the same value for that column);
• other columns are a problem, because the rows in the group might have different values in them.
  In standard SQL, such columns are forbidden; SQLite allows them, but just gives you values from any random row in the group, which is almost never what you want.
  Beginning with SQLite 3.7.11, you get values from the row that matches a MIN or MAX; this is what you see in SQLite Exprert, but not on Androids with an older SQLite.

---

To solve your problem, you have to first use a GROUP BY to get enough information to identify the records you want:

SELECT smsCONID,                            -- OK: used in GROUP BY
       MAX(smsTIMESTAMP) AS smsTIMESTAMP,   -- OK: aggregate MAX
       COUNT(*) AS smsNUMMESSAGES           -- OK: aggregate COUNT
FROM sms
GROUP BY smsCONID
ORDER BY smsTIMESTAMP DESC

Then, join that result table with the original sms table to get the other columns of these records:

SELECT *
FROM (SELECT smsCONID,
             MAX(smsTIMESTAMP) AS smsTIMESTAMP,
             COUNT(*) AS smsNUMMESSAGES
      FROM sms
      GROUP BY smsCONID) AS grouped
     JOIN sms
       ON grouped.smsCONID     = sms.smsCONID
      AND grouped.smsTIMESTAMP = sms.smsTIMESTAMP
ORDER BY smsTIMESTAMP DESC