How do get records from different using webservices?

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C#

SQL-Server

Here is my Database diagram and my scenario is that When a user enter number of person and amount, amount/person
let suppose 4/1000=250 and now 250 is , match in Product_Price Field in RstProductDetails, and select only Restaurant where 250 is matched. Next when a user select Restaurant e.g KFC and then KFC Products details is show.
Here is my [WebMethod]

    [WebMethod]
    public DataSet Restaurant(string Amount, string PersonHash)
    {
//        DataSet result = Amount / personHash;

        DataSet result = null;
        const string SQL_COMMAND_TEXT = "SELECT Rst_Name FROM RstProductDetails WHERE Product_Name WHERE Product_rice<=250 = @Rst_Name";
        using (SqlConnection connection = Class1.GetConnection())
        {
            connection.Open();
            using (SqlCommand command = new SqlCommand(SQL_COMMAND_TEXT, connection))
            {
                command.Parameters.Add("@Rst_Name", SqlDbType.NVarChar);
                command.Parameters.Add("@PersonHash", SqlDbType.NVarChar);
                command.Parameters["@Rst_Name"].Value = Amount;
                command.Parameters["@PersonHash"].Value = PersonHash;
                using (SqlDataAdapter dataAdapter = new SqlDataAdapter(command))
                {
                    result = new DataSet();
                    dataAdapter.Fill(result);
                }
            }
        }

        return result;
    }