获取记录的主键标识符值 (SQL)

Question

I have been working on a school project- an app. I've been using an sql db for my database. For one particular task, I wanted to use the customer's username (which is unique) to find the corresponding customer_id value (an auto increment integer primary key) for other purposes. The code I used looked like this:

public int getCustomerid(String username){

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor resultset = db.rawQuery("SELECT cust_code FROM Customer where username='" + username+ "'", null);
        resultset.moveToFirst();
        return resultset.getInt(0);
    }

I have used this format of queries for obtaining other values like password, email id, etc. However, when I try to use this method to extract the primary key value, I get a null pointer exception error. Is there any way to solve this?

Thanks,

Answer 1

I do not know why this works:

public int getCustomerid(String username){

    SQLiteDatabase db = this.getWritableDatabase();
    String SQLquery = "SELECT cust_code FROM Customer where username='" + username+ "'"
    Cursor resultset = db.rawQuery(SQLquery, null);
    resultset.moveToFirst();
    return resultset.getInt(0);
}

I now see how creating parameters adds more clarity. Thank you very much Mr. Gordon Linoff.