Joining tables in LINQ/SQL - sql

Question

I have below a collection of rows and each row consists of productid, unitid, countryid.
I need to find the details for each row in the corresponding tables (products, units, country)
for product - select product name, updatedby
for unitid - select unit name , updatedby
for countryid - select countryname, uploadby
and returning the rows which has the same format
Id = product id or unitid or countryid
name = proudct name or unit name or countryname
modified = product updatedby or unit updated by or country uploadby
So, in summary -
1. For a Collection of rows
a. use the id to get the extra details from the respective table
b. return the same type of collection for the results
2. do step 1 for
2.a For RegularToys (Run this logic on TableBigA)
2.b For CustomToys(Run this logic on TableB)
3. Return all the rows
by adding 2.a and 2.b
How to write an sql/linq query for this? thanks

Answer 1

If I'm understanding correctly, you want to use a given ID to find either a product, a unit or a country but you're not sure which. If that's the case, then you can build out deferred queries like this to find the given entity:
var prod = from p in db.Products
where p.ProductId = id
select new { Id = p.ProductId, Name = p.ProductName, Modified = p.UpdatedBy };
var unit = from u in db.Units
where p.UnitId = id
select new { Id = u.UnitId, Name = u.UnitName, Modified = p.UpdatedBy };
var ctry = from c in db.Countries
where c.CountryId = id
select new { Id = c.CountryId, Name = c.CountryName, Modified = c.UploadBy };
And then execute the queries until you find an entity that matches (with ?? being the null-coalesce operator that returns the right value if the left result is null).
var res = prod.SingleOrDefault() ??
unit.SingleOrDefault() ??
ctry.SingleOrDefault() ??
new { Id = id, Name = null, Modifed = null };

Answer 2

Without any further details I can't be more specific about the condition below, but I think you are asking for something along these lines. I'm assuming your Id's are int's (but this can be easily changed if not) and you already have an Entity Data Model for the tables you describe.
Create a class for your common data:
class RowDetail
{
public int Id { get; set; }
public string Name { get; set; }
public string Modified { get; set; }
}
Pull the information out of each of the sub tables into a new record:
IEnumerable<RowDetail> products =
from p in db.Products
where <<CONDITION>>
select
new RowDetail()
{
Id = p.ProductId,
Name = p.ProductName,
Modified = p.UpdatedBy
};
IEnumerable<RowDetail> units =
from u in db.Units
where <<CONDITION>>
select
new RowDetail()
{
Id = u.UnitId,
Name = u.UnitName,
Modified = u.UpdatedBy
};
IEnumerable<RowDetail> countries =
from c in db.Countries
where <<CONDITION>>
select
new RowDetail()
{
Id = c.CountryId,
Name = c.CountryName,
Modified = c.UploadBy
};
Finally pull all the records together in a single collection:
IEnumerable<RowDetail> results = products.Union(units).Union(countries);
I'm not sure if this is exactly what you are looking for, so feel free to give feedback and/or more details if further assistance is required.