android.database.sqlite.SQLiteException: near ")": syntax error (code 1):

 public String getProductName(double id) {  
        database = DBHelper.getReadableDatabase(); // open database to perform some operation   
 
        Cursor c = database.rawQuery("SELECT " + COL_PRODUCT_NAME + " FROM " 
                + TABLE_PRODUCT + " WHERE " + COL_CATEGORY + "=  " + id +" ", null);  
                  
 
                if(c.moveToFirst())  
                {   
                    String strCatName = c.getString(c.getColumnIndex(COL_PRODUCT_NAME));  
                     c.close();  
                     database.close();  
                    return strCatName;  
                  }  
                else   
                {  
                    return "";  
                    }  
        } 
 public String getProductName(double id) {
     database = DBHelper.getReadableDatabase(); // open database to perform some operation

     Cursor c = database.rawQuery("SELECT " + COL_PRODUCT_NAME + " FROM "
          + TABLE_PRODUCT + " WHERE " + COL_CATEGORY + "=  " + id +" ", null);
          

          if(c.moveToFirst())
          {
                 String strCatName = c.getString(c.getColumnIndex(COL_PRODUCT_NAME));
                  c.close();
                  database.close();
                 return strCatName;
               }
          else
          {
           return "";
           }
     }

Here's the problem :

07-14 16:51:15.683: E/AndroidRuntime(1497): Caused by: android.database.sqlite.SQLiteException: near ")": syntax error (code 1): , while compiling: SELECT COUNT(*) FROM table_product WHERE category = '3')