(1) near null syntax error

04-24 12:15:21.671: E/AndroidRuntime(26419): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.flocator/com.flocater.Friendfinderactivity}: android.database.sqlite.SQLiteException: near "null": syntax error (code 1): , while compiling: select * from null

This is the error I am getting every time I am trying to compile..I am a learning android so I don't know much about this...so can anyone help me to fix this issue.. and I am also getting error "Source not found" so can you help me to sort out with these two problems.

The codes are In Friendfnderactivity.java package com.flocater;

import com.flocator.R;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;



public class Friendfinderactivity extends Activity {
/** Called when the activity is first created. */
public static String deviceid = "deviceid";

public static String device_id = "device_id";
public static String user_id = "user_id";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    DBHelper dbhelper = new DBHelper(this);
    SQLiteDatabase db = dbhelper.getWritableDatabase();

    TelephonyManager tm = (TelephonyManager) this
            .getSystemService(Context.TELEPHONY_SERVICE);

    deviceid = tm.getDeviceId();

    Cursor cursor = db.rawQuery("select * from "
            + Database.SUBSCRIBE_TABLE_NAME, null);

    int rows = cursor.getCount();

    if (rows > 0) {
        cursor.moveToFirst();
        user_id = cursor.getString(0);
        device_id = cursor.getString(3);
    }
    db.close();
    if (device_id.equals(deviceid)) {
        setContentView(R.layout.subscriber);
    } else
        setContentView(R.layout.subscribe);
 }

public void subscribeUser(View v) {
    // get access to views
    EditText editName = (EditText) this.findViewById(R.id.editName);
    EditText editPhone = (EditText) this.findViewById(R.id.editPhone);
    EditText editArea = (EditText) this.findViewById(R.id.editArea);
    EditText editCity = (EditText) this.findViewById(R.id.editCity);

    boolean done = Database.addUser(this, editName.getText().toString(),
            editPhone.getText().toString(), deviceid, editArea.getText()
                    .toString(), editCity.getText().toString());

    if(done) {
        Toast.makeText(this, "Subscribed Successfully!",   Toast.Length_Long).show(); 
        Intent intent = new Intent(this,Friendfinderactivity.class);
        startActivity(intent);
    }
    else
        Toast.makeText(this, "Sorry! Could not subscribe!",                             Toast.LENGTH_LONG).show();
}

public void addFriends(View v) {
    Intent intent = new Intent(this,AddFriends.class);
    startActivity(intent);
}

public void viewFriends(View v) {
    Intent intent = new Intent(this,SeeFriends.class);
    startActivity(intent);
}

}