Android sqlite how to check if a record exists

Question

I would like to check whether a record exists or not.

Here is what I've tried:

MainActivity.class

    public void onTextChanged(CharSequence s, int start, int before, int count) {          System.out.println("Ontext changed " + new String(s.toString()));         strDocumentFrom = s.toString();                   if(s.toString().isEmpty()){          } else {               try{                  strTransactionDate = dbHelper.getTransactionDateByDocumentNumber(strDocumentFrom);                  //strTotalAmount = dbHelper.getTotalAmountByDocumentNumber(strDocumentFrom);                  //strVan = dbHelper.getVanByDocumentNumber(strDocumentFrom);                    //etTransactionDate.setText(strTransactionDate);                  //etTotalAmount.setText(strTotalAmount);                  //Log.d("Van", "" + strVan);                  //etVan.setText(strVan);               } catch (SQLiteException e) {                  e.printStackTrace();                  Toast.makeText(ReceivingStocksHeader.this,                           "Document number does not exist.", Toast.LENGTH_SHORT).show();              }          } 

DBHelper.class

            // TODO DISPLAYING RECORDS TO TRANSRCVHEADER         public String getTransactionDateByDocumentNumber(String strDocumentNumber){             String[] columns = new String[]{KEY_TRANSACTIONDATE};              Cursor c = myDataBase.query(TBL_INTRANS,                      columns, null,                      null, null, null, null, null);              if(c != null){                 c.moveToFirst();                 String date = c.getString(0);                 return date;             } else {                 Log.d("Error", "No record exists");             }               return null;         } 

But it doesn't get it to the catch block to display the toast.

What am I doing wrong in here?

Answer 1

public static boolean CheckIsDataAlreadyInDBorNot(String TableName,         String dbfield, String fieldValue) {     SQLiteDatabase sqldb = EGLifeStyleApplication.sqLiteDatabase;     String Query = "Select * from " + TableName + " where " + dbfield + " = " + fieldValue;     Cursor cursor = sqldb.rawQuery(Query, null);         if(cursor.getCount() <= 0){             cursor.close();             return false;         }     cursor.close();     return true; } 

I hope this is useful to you... This function returns true if record already exists in db. Otherwise returns false.

Answer 2

These are all good answers, however many forget to close the cursor and database. If you don't close the cursor or database you may run in to memory leaks.

Additionally:
You can get an error when searching by String that contains non alpha/numeric characters. For example: "1a5f9ea3-ec4b-406b-a567-e6927640db40". Those dashes (-) will cause an unrecognized token error. You can overcome this by putting the string in an array. So make it a habit to query like this:

public boolean hasObject(String id) {     SQLiteDatabase db = getWritableDatabase();     String selectString = "SELECT * FROM " + _TABLE + " WHERE " + _ID + " =?";      // Add the String you are searching by here.      // Put it in an array to avoid an unrecognized token error      Cursor cursor = db.rawQuery(selectString, new String[] {id});       boolean hasObject = false;     if(cursor.moveToFirst()){         hasObject = true;          //region if you had multiple records to check for, use this region.           int count = 0;         while(cursor.moveToNext()){           count++;         }         //here, count is records found         Log.d(TAG, String.format("%d records found", count));          //endregion      }       cursor.close();          // Dont forget to close your cursor     db.close();              //AND your Database!     return hasObject; }