how to check if the column of a SQLite dabase is null

Question

i am not able to get a reliable result to tell if the collumn of a database is null or not. i tried using a query checking to see if the the column of the database returns null or a string value of "" but no matter what i do the result of my check returns a result that there is something stored in that column, even if it is empty.

to make sure it is empty i delete all the data from the app and uninstall it from the device. that way i know the database column is empty

is there a better way to check if a particular column is empty?

if a column has never been used before on a newly created database, what is in that column? is it null or is there something put in by the system as a placeholder?

displayAll.setOnClickListener(new View.OnClickListener() {

    public void onClick(View v) {

        textToShow.setText(DisplayAllFieldsObjectFromDB());
        if (DisplayAllFieldsObjectFromDB() == null) {
            Toast.makeText(DisplayTable.this, "TABLE NULL ", Toast.LENGTH_SHORT).show();

        } else if (DisplayAllFieldsObjectFromDB() != null) {
            Toast.makeText(DisplayTable.this, "TABLE HOLDS A VALUE ", Toast.LENGTH_SHORT).show();

        } else if (DisplayAllFieldsObjectFromDB().equals("")) {
            Toast.makeText(DisplayTable.this, "TABLE HOLDS EMPTY QUOTES VALUE ", Toast.LENGTH_SHORT).show();
        }

    }
});

code from the database table

// display all data from table
public String getAllFromDB() {

    String tableString = "";

    String result = "";
    Cursor cursor = sqLiteDatabase.query(MYDATABASE_TABLE, null,
        null, null, null, null, null);
    if (cursor != null) {
        // cursor.moveToFirst(); // use only this for getting one row
        while (cursor.moveToNext()) { // use only this for getting multiple rows
            tableString = cursor.getString(cursor.getColumnIndex(TABLE_STRING));
            result += tableString + "\n";
        }
    }    
    return result;    
}

Answer 1

Read the documentation: the cursor object has an isNull function.