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Update one table using self-join for other table

I have two tables. I need to update the records of the 1st table performing a join with the 2nd table. But in the 2nd table I also have to put a self join.
UPDATE [T2]
SET T2.NAME = T1.NAME
FROM [TABLE2] T2
JOIN [TABLE1] T1 ON T2.ID = T1.ID
JOIN [TABLE1] T3 ON T1.RECORDTYPE = T3. RECORDTYPE
The purpose is to perform a self-join and update the other table.

Is this what you mean?
UPDATE T2
SET T2.NAME = T1.NAME
FROM T2
JOIN T1
ON T2.ID = T1.ID
AND T2.RECORDTYPE = T1.RECORDTYPE;

How to apply Right Outer Join using LINQ in C#?

I am facing issue to apply Right Outer Join in LINQ. I am trying to build the similar query in LINQ by converting from SQL query.
My correct SQL query
select *
from Table1 t1
inner join Table2 t2 on t1.Id = t2.FID and t1.CID = 20
right outer join Table3 t3 on t1.GID = t3.GID
var result = from t1 in Table1
join t2 in Table2
on t1.ID equals t2.FID into gr1
where t1.CID = 20
join t3 in Table3
on t1.GID equals t3.GID into gr2
from t3 in gr2.DefaultIfEmpty()
select new Details (){
}
return result.ToList();
}
My LINQ query is not working as expected to SQL query.

This is also discussed here
how to make a right join using LINQ to SQL & C#
var RightJoin = from adds in dc.EmpresaAddendas
join cats in CatAddendas
on adds.IDAddenda equals cats.IDAddenda into joined
from cats in joined.DefaultIfEmpty()
select new
{
Id = cats.IDAddenda,
Description = cats.Descripcion
};

Try this:
var result = from t1 in Table1
join t2 in Table2
on new { id = t1.ID; cid = t1.CID } equals new { id = t2.FID: cid = 20} into gr1
join t3 in Table3
on t1.GID equals t3.GID into gr2
from t123 in gr2.DefaultIfEmpty()
select new Details (){
}
return result.ToList();
}

As you're discovered, most LINQ providers don't offer support for a right join. DefaultIfEmpty translates into a LEFT join. As a result, you need to flip the logic of your query around a bit to turn the right join into a left one.
As far as the actual syntax, I've had success adopting more of an ANSI-82 syntax rather than worrying about the into temp2 from temp3 in temp2 syntax. Something along the lines of:
var result =
from t3 in Table3
from t1 in Table1.Where(temp1 => temp1.GID == t3.GID).DefaultIfEmpty()
join t2 in Table2 on t1ID equals t2.FID
where t1.CID == 20
select new Details{};

c# I need to perform this SQL Select to LINQ

I have this Select:
SELECT (MyFields)
FROM table1 T1
INNER JOIN table2 t2 ON t2.ID_t2 = T1.ID_T1
INNER JOIN
table3 t3 on t3.ID_t3=T1.ID_T1 and Left(t3.Other_t3_field,5)=t2.Another_t2_field
WHERE (Conditions)
Then, I tried in C#:
var query = from T1 in table1
join t2 in table2 on T1.ID_T1 equals t2.ID_t2
join t3 in **table3** on T1.ID_T1 equals v.ID_t3
join t4 in **table3** on t2.Other_t2_field equals Microsoft.VisualBasic.Strings.Left(t2.Another_t3_field, 5)
where (Conditions)
select new
{
(My fields)
};
Both works, but my C# query have more results then SQL Select, I don't know what I am doing wrong?

Well I'd start by changing the join on table 3 in the C# - use an anonymous type to join on multiple fields:
join t3 in table3 on new { Id = t1.ID_T1, X = t2.AnotherT2Field.Substring(0, 5) }
equals new { Id = t3.ID_T3, X = t3.OtherT3Field.Substring(0, 5) }
(I'd hope you can use Substring instead of Left here... it's much more idiomatic C#.)

You can add multiple join conditions with an anonymous type:
var query = from T1 in table1
join t2 in table2 on T1.ID_T1 equals t2.ID_t2
join t3 in **table3** on new {
ID = T1.ID_T1,
substring = t2.Other_t2_field
} equals new
{
ID = v.ID_t3,
substring = Microsoft.VisualBasic.Strings.Left(t2.Another_t3_field, 5)
}
where (Conditions)
select new
{
(My fields)
};
As Jon Skeet mentioned: you can also use Substring instead of Left.

How to join table with multiple columns in linq?

I have following code in linq, what I am trying to do is joining tables with multiple columns of one table
//NOT A VALID CODE
from t1 in table1
join t2 in table2 on ((t1.ID equals t2.orderId) || (t1.ID equals t2.pickupId ))// how can I do this
...
...
How can I achieve this in Linq?

Use an anonymous type
from t1 in table1
join t2 in table2 on new { t1.ID, t1.pickupId } equals new { t2.ID, t2.pickupId }
...

var query = from t1 in table1
from t2 in table2
where t1.ID == t2.orderId || t1.ID == t2.pickupId
select new { t1, t2};

Join Two DataTables (Some Rows Match some Don't)

I have two Data Tables: T1 and T2
T1 and T2 both have a Column Registration, but T2 doesn't have all the same Rows as T1.
I have to combine the Two Tables such that if the Registration Number is same get columns from T2, if not show Blank, but I need ALL ROWS FROM T1, (IF MATCH OR NOT).
I tried this but I only get matching Rows:
var results = from table1 in T1
join table2 in T2
on (String)table1["Registration"] equals (String)table2["Registration"]
select new
{
Registration = (String)table1["Registration"],
DistanceInKM = (decimal)table1["DistanceInKM"],
TotalDistanceTravelledKM = (Double)table2["TotalDistanceTravelledKM"]
};

You're performing an inner join, which only shows rows that exist on both sides.
Try using a left outer join instead:
var results = (from table1 in T1.AsEnumerable()
join tmp in T2.AsEnumerable() on table1["Registration"] equals tmp["Registration"] into grp
from table2 in grp.DefaultIfEmpty()
select new
{
Registration = (String)table1["Registration"],
DistanceInKM = (decimal)table1["DistanceInKM"],
TotalDistanceTravelledKM = (table2 == null ? (double?)null : (Double)table2["TotalDistanceTravelledKM"])
};