Question

i wan to retrieve data from query involving many tables.
i have a query as follows

    String sql = "SELECT "
            + "s.Food_ID AS 'Sales_FoodID', "
            + "f.Food_Name AS 'foodName' "
            + "FROM Ordering o, Sales s, Food f"
            + " WHERE o.Table_No = " + tableNo + ""
            + " AND o.Paid = '" + NOT_PAID + "'"
            + " AND s.Order_ID = o.Order_ID"
            + " AND f.Food_ID = s.Food_ID;";
    resultSet = statement.executeQuery(sql);

no error were found when i run the program, but after i add this line to get a table’s column data:

    String orderID = resultSet.getString("foodName");

i’m given this error:

    java.sql.SQLException: Column not found

anyone know why?

Answer 1

You have to use next() method.

You should know that ResultSet is implicitly positioned on position before first row so you need to call next to get current position and if is valid, it returns true, else returns false (cursor is positioned after the last row).

rs = statement.executeQuery(sql);
while (rs.next()) {
   String orderID = rs.getString(2);
}

Note: You can use also rs.getString(<columnName>) but in case when you know how your statement looks i recommend to you use index instead of columnName.