Как linq query извлекает данные из нескольких таблиц без использования join?

I have 3 tables in my database which have no relation with each other. what i want is to implement the search operation on my website. So that when a word is submit in search box the query go through all the tables and fetch the data wherever it find that word. I can fetch the data from single table.

Please don't confuse about what i return in action method, its a very long and unnecessary code for that question.

By using this code I successfully get the search result from one table. Now I want same result from all the tables present in the database. that's where I'm stuck. I searched so many article for that but didn't find any solution that's in the last I myself asking this.

Thanks

public PartialViewResult Searchpartial(string searchString)
		{

			
			var article = (from c in db.Tbl_Article select new 
                        SearchModel() { Tbl_Article = c });
			article = article.Where(s => 
                      s.Tbl_Article.Article_Title.Contains(searchString));

			var blog = (from c in db.Tbl_Blog select new SearchModel() { 
                        Tbl_Blog = c });
			blog = blog.Where(s => 
                             s.Tbl_Blog.Blog_Title.Contains(searchString));
 
			var history = (from c in db.Tbl_History select new 
                        SearchModel() { Tbl_History = c });
			history = history.Where(s => 
                          s.Tbl_History.Title.Contains(searchString));

			var result = article.Select(x => 
                            x.Tbl_Article.Article_Title).Union(blog.Select(x => 
                          x.Tbl_Blog.Blog_Title)).Union(history.Select(x => 
                              x.Tbl_History.Title)).ToList();
				

		
			


			if (result != null)
			{
				return PartialView("Searchpartial", result);
			}
			else
			{
				string res = "No Record Found";
				return PartialView("Searchpartial", res);
			}

		}

        @model IEnumerable<project.Models.SearchModel>
             @using Project.Models
           <div class="col-md-8">
            	@{


		if (Model.Count() == 0)
		{<br />
			<br />
			<br />
			<div class="col-md-12">
				<p>
					Sorry! No result found
				</p>
			</div>
		}
		else
		{<br />
			<br />
			<br />
			foreach (var item in Model)
			{

				<div class="col-md-12">
					<p>

		<a href="@Url.Action("Article","ArticleView", new { id = 
                           HttpUtility.UrlEncode(new 
                      StandardModule().Encrypt(item.Tbl_Article.Id.ToString())) 
                        })">@item.Tbl_Article.Article_Title</a>
		<a  href="@Url.Action("Blog","BlogView", new { id = 
                      HttpUtility.UrlEncode(new 
                    StandardModule().Encrypt(item.Tbl_Blog.Id.ToString())) 
                              })">@item.Tbl_Blog.Blog_Title</a>
		<a href="@Url.Action("History","HistoryView", new { id = 
                      HttpUtility.UrlEncode(new 
                      StandardModule().Encrypt(item.Tbl_History.Id.ToString())) 
                      })">@item.Tbl_History.Title</a>
					</p>
				</div>
			}
		}

	}
</div>

public class SearchModel
	{
		public Tbl_Article Tbl_Article { get; set; }
		public Tbl_Blog Tbl_Blog { get; set; }
		public Tbl_History Tbl_History { get; set; }	

	}