从Linq2Sql中的3个表中提取记录

Question

I have got 3 tables in my database. Company, Product and Lead. Below are my fields.

Leads Table:

SELECT [Id]
      ,[BuySellTypeId]
      ,[ProductName]
      ,[Keywords]
      ,[CategoryId] // categoryid
      ,[SubCategoryId]
      ,[Description]
      ,[ProductImagePath]
      ,[CreationDate]
      ,[ExpiryDate]
      ,[CompanyId] // company id
      ,[ShortDescription]
      ,[IsExpired]
      ,[IsActive]
  FROM [BuySell]

Products Table:

SELECT   
        Id, 
        Name, 
        Description, 
        ImagePath, 
        CompanyId, //company id
        Keywords, 
        CategoryId,  // categoryid
        SubCategoryId, 
        PostedDate, 
        ExpiryDate, 
        ShortDescription, 
        IsActive,                       
        IsExpired
FROM  Products

I have one more table " Company " whose reference is shown above in the two tables. My requirement is to pull out all companies that exists in above tables, Products and BuySell in same categories. For example If I want to see all companies of CategoryId = 15, then it will pull all companies with categoryid= 15 from buysell and products table. Obviously there will be redundancy, so i will use Distinct() to extract distinct items.

My Linq2Sql Biz layer method

        /// <summary>
        /// Returns all companies by category id that exists in Lead and Products
        ///table
        /// </summary>
        /// <param name="categoryId">category id as integer</param>
        /// <param name="take">records to take</param>
        /// <param name="skip">records to skip</param>
        /// <returns>List of companies</returns>
        public static IList GetCompaniesByCategory(int categoryId, int take, int skip)
        {
            return (from c in Context.Companies
                   join bs in Context.BuySells on c.CompanyId equals bs.CompanyId
                   join p in Context.Products on c.CompanyId equals p.CompanyId
                   where bs.CategoryId == categoryId || p.CategoryId==categoryId
                   select new
                              {
                                  c.CompanyId,
                                  c.CompanyName,
                                  c.Country.Flag,
                                  c.Profile,
                                  c.IsUsingSMSNotifications,
                                  c.IsVerified,
                                  c.MembershipType,
                                  c.RegistrationDate, c.ShortProfile,
                              }).Skip(skip).Take(take).Distinct().ToList();
        }

But the above code return me 0 items. When i design its sql , see below,

SELECT     dbo.Company.CompanyId, dbo.Company.CompanyName, dbo.Company.Name, dbo.Company.IsVerified, dbo.Company.IsUsingSMSNotifications, 
                      dbo.Company.CompanyLogo, dbo.Company.RegistrationDate, dbo.Company.Profile
FROM         dbo.BuySell INNER JOIN
                      dbo.Company ON dbo.BuySell.CompanyId = dbo.Company.CompanyId LEFT OUTER JOIN
                      dbo.Products ON dbo.Company.CompanyId = dbo.Products.CompanyId
WHERE     (dbo.BuySell.CategoryId = 1) AND (dbo.Products.CategoryId = 1)

i am able to get the company from BuySell but not from Product. So please help me. I need the LINQ equivalent statement. To replace the above cs code.

Answer 1

If you have any relation between those tables, the query might be much simpler

return (from c in Context.Companies
where c.BuySells.Any( b=>b.CategoryId == categoryId)
      || c.Products.Any( p=>p.CategoryId == categoryId)
select new
{
  c.CompanyId,
  c.CompanyName,
  c.Country.Flag,
  c.Profile,
  c.IsUsingSMSNotifications,
  c.IsVerified,
  c.MembershipType,
  c.RegistrationDate, c.ShortProfile,
}).Skip(skip).Take(take).ToList();

The query used with SSMS checks for CategoryId = 1 and uses an AND condition, but your LINQ query uses an OR condition