Optimizing SQL Server Performance Using Indexes

CREATE TABLE "maintable"(
"ID" INT NOT NULL IDENTITY (1, 1) PRIMARY KEY,
"name" NVARCHAR (50) NULL,
"description" NVARCHAR (100) NULL
)
CREATE TABLE "secondtable" (
"ID" INT NOT NULL IDENTITY (1, 1) PRIMARY KEY,
"sname" NVARCHAR (50) NULL,
"sdescr" NVARCHAR (100) NULL,
"somefirstnumber" INT DEFAULT 0,
"somesecondnumber" INT DEFAULT 1,
"somedatetime" DATETIME NOT NULL,
"howmanyhours" INT NULL DEFAULT 0,
"newdate" AS DATEADD(HOUR, "howmanyhours", "somedatetime"),
"mainID" INT NOT NULL
CONSTRAINT FK_SecondToMain FOREIGN KEY ("mainID")
REFERENCES "maintable" ("ID")
);
--Хранимые процедуры
CREATE PROCEDURE "insertintomain"
@Name NVARCHAR (50), @Descr NVARCHAR (100)
AS
	INSERT INTO "SimpleIndex"."dbo"."maintable" ("name", "description")
	VALUES (@Name, @Descr);
GO
CREATE PROCEDURE "insertintosecond"
@Sname NVARCHAR(50), @Sdescr NVARCHAR(100),
@Firstnumber INT, @Secondnumber INT,
@SomeDT DATETIME, @Hours INT, @MainID INT
AS
	INSERT INTO "SimpleIndex"."dbo"."secondtable" (
	"sname", "sdescr", "somefirstnumber", 
	"somesecondnumber", "somedatetime", 
	"howmanyhours", "mainID")
	VALUES (
	@Sname, @Sdescr,@Firstnumber, @Secondnumber,
	@SomeDT, @Hours, @MainID)
GO

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.SqlClient;
namespace SimpleAddingRandomRecordsToDatabase
{
    class Program
    {
        static string alphabet()
        {
            //Количество пробелов означает частоту их появляния
            string alphabet = "abcdefgh ijklmnopqrst uvwxyzабвгд еёжзийкл мнопросту фхцчшщыэюя ";
            //преобразуем алфавит в юникод
            Encoding enc = Encoding.UTF8;
            var bytes = enc.GetBytes(alphabet);
            alphabet = enc.GetString(bytes);
            return alphabet;
        }
        static int alphlen = alphabet().Length;
        static string getRandomString(int lenth, int rndparam, bool allowspacebars)
        {
            string str = "";
            Random rand = new Random(rndparam);
            for (int i = 0; i < lenth; i++)
            {
                int num = rand.Next(alphlen);
                str = str + alphabet()[num];
            }
            if (!allowspacebars)
            {
                str = str.Replace(" ", "");
            }
            return str;
        }
        static void Main(string[] args)
        {
            string result;
            Console.WriteLine("Нажмите 1 для начала операции");
            result = Console.ReadLine();
            if (result.Equals("1"))
            {
                //Подключаемся к БД
                SqlConnection cn = new SqlConnection();
                SqlConnectionStringBuilder cs = new SqlConnectionStringBuilder();
                cs.IntegratedSecurity = true;
                cs.DataSource = @"KONSTANTIN\KONSTANTINSQL";
                cs.InitialCatalog = "SimpleIndex";
                cn.ConnectionString = cs.ToString();
                cn.Open();
                //генерируем первые 10 000 записей для главной таблицы
                int i2 = 0;
                for (int i = 0; i < 10000; i++)
                {
                    SqlCommand cm = cn.CreateCommand();
                    cm.CommandType = CommandType.StoredProcedure;
                    cm.CommandText = "insertintomain";
                    i2++;
                    cm.Parameters.Add(new SqlParameter("Name", getRandomString(50, i2, false)));
                    i2++;
                    cm.Parameters.Add(new SqlParameter("Descr", getRandomString(100, i2, true)));
                    cm.ExecuteNonQuery();
                }
                //Генерируем 1 000 000 записей, соедниённых с первой таблицей
                i2 = 0;
                for (int i = 0; i < 1000000; i++)
                {
                    Random rand = new Random();
                    DateTime dt = DateTime.Now;
                    dt = dt.AddHours((-1) * rand.Next(2000));
                    SqlCommand cm = cn.CreateCommand();
                    cm.CommandType = CommandType.StoredProcedure;
                    cm.CommandText = "insertintosecond";
                    i2++;
                    cm.Parameters.Add(new SqlParameter("Sname", getRandomString(50, i2, false)));
                    i2++;
                    cm.Parameters.Add(new SqlParameter("Sdescr", getRandomString(100, i2, true)));
                    i2++;
                    Random rand2 = new Random(i2);
                    cm.Parameters.Add(new SqlParameter("Firstnumber", rand2.Next(10000)));
                    i2++;
                    rand2 = new Random(i2);
                    cm.Parameters.Add(new SqlParameter("Secondnumber", rand2.Next(100)));
                    cm.Parameters.Add(new SqlParameter("SomeDT", dt));
                    i2++;
                    rand = new Random(i2);
                    cm.Parameters.Add(new SqlParameter("Hours", rand.Next(30)));
                    i2++;
                    rand = new Random(i2);
                    cm.Parameters.Add(new SqlParameter("MainID", rand.Next(9999)+1));
                    cm.ExecuteNonQuery();
                }
                cn.Close();
                Console.WriteLine("Данные вставлены.");
            }
        }
    }
}