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How to make a JOIN in LINQ to SQL equivalent to Not Equals

I've got a table:
Year | Period | Account
During a new period, I'd like to get a list of new accounts and a list of accounts that also existed in the prior period.
Accounts that are also in the prior period:
bs.DataSource = from c in accountsToImport
join p in accountsToImport on c.Account equals p.Account
where c.Year == year && c.Period == period
&& p.Year == priorYear && p.Period == priorPeriod
select c;
return bs;
However, I can't figure out how to get the equivalent of "not equals p.account" with LINQ->SQL. The SQL command that does work:
select * from tsr_accountsToimport as cper
inner join tsr_accountstoimport as pper
on cper.account <> pper.account
where
cper.year = 2015
and cper.period = 4
and pper.period = 3
Any help to get the LINQ syntax would be greatly appreciated. Thanks!

You can try SelectMany instead of join.
from c in accounts
from p in accounts
where c.Account != p.Account

Convert shown query/subquery to group by?

Update: I have got a sql query working but am still having trouble converting it to linq2sql. Please see the code below..
I have a linq query that is pulling a lot of data but sometimes it times out due to the load it puts on the sql server. I am going to work on getting more efficient data (adding indexes etc) but I have also heard that using group by would be more efficient than using the sub query. Would a group by be more efficient and if so what would my query below look like with a group by? I am not familiar with group by yet. Please dont use lambda
Edit: New query which is still slow and can time out:
var query = (from s in db.ZipCodeServiceAvailabilities
join a in db.pdx_apart_views on s.ZipCode equals a.Zip_Code.Substring(0, 5) into a_join
from a in a_join.DefaultIfEmpty()
join b in db.ZipCodeBoundaries on s.ZipCode equals b.ZipCode into b_join
from b in b_join.DefaultIfEmpty()
where
(s.IsServiced == 1 &&
b.Ordering % 10 == 0 &&
s.State == "AL")
group new { s, b, a } by new
{
s.ZipCode,
s.IsServiced,
b.Longitude,
b.Latitude,
b.Ordering
} into g
orderby
g.Key.ZipCode,
g.Key.Ordering
select new
{
g.Key.ZipCode,
apartCount = g.Count(p => p.a.Apartment_complex != null),
Longitude = g.Key.Longitude,
Latitude = g.Key.Latitude
}).ToArray();
Edit: Query working in sql that I want in linq2sql (very fast):
select s.ZipCode, count(distinct ident) ApartCount, b.Longitude, b.Latitude from ZipCodeServiceAvailability s
left join pdx_apart_view
on s.ZipCode = left([Zip Code], 5)
left join ZipCodeBoundaries b
on s.ZipCode = b.ZipCode
Where IsServiced = 1 and and Ordering % 10 = 0 and State = 'AL'
Group By s.ZipCode, IsServiced, b.Longitude, b.Latitude, b.Ordering
Order by s.ZipCode, b.Ordering
Original query that is very slow:
var zips = (from s in db.ZipCodeServiceAvailabilities
join b in db.ZipCodeBoundaries on s.ZipCode equals b.ZipCode
where (s.IsServiced == service
&& b.Ordering % 10 == 0
&& s.State.Contains(state))
orderby b.ZipCode
select new
{
zipCode = b.ZipCode.Trim(),
latitude = b.Latitude,
longitude = b.Longitude,
apartCount = (from a in db.pdx_apart_views
where a.Zip_Code.Remove(5) == b.ZipCode
select a.Apartment_complex).Count()
}).ToArray();

Do you mean that you are not familiar with grouping in general, or only in the linq context?
I find it easier to write plain SQL than linq when I don't have the entity definitions, and below is what I think you are looking for in SQL - converting back to linq should be fairly straight-forward.
select
b.ZipCode zipCode,
b.Latitude latitude,
b.Longitude longitude,
count(a.Apartment_complex) apartCount
from
ZipCodeServiceAvailabilities s
join ZipCodeBoundaries b
on s.ZipCode = b.ZipCode
left join pdx_apart_views a
on substring(a.Zip_Code, 1, 5) = b.ZipCode
group by
ZipCode,
Latitude,
Longitude

There was no way to duplicate the left[(zip code), 5] sql method in linq2sql without breaking the index. The answer was to go with straight ado.net so I get all sql functionality.

Get Count from one value in three table linq2sql select?

I just want the apartment complex count along with the other values. Only adding the count breaks the code. The error I get is "Sequence operators not supported for type 'System.String'." I have also tried changing apartCount to an int with no luck. Any help would be appreciated
using (var db = new DataClasses2DataContext())
{
var zips = (from s in db.ZipCodeServiceAvailabilities
join b in db.ZipCodeBoundaries on s.ZipCode equals b.ZipCode
join a in db.pdx_apart_views on s.ZipCode equals a.Zip_Code
where (s.IsServiced == 1 && b.Ordering % 10 == 0)
orderby b.ZipCode
select new
{
zipCode = b.ZipCode.Trim(),
latitude = b.Latitude,
longitude = b.Longitude,
apartCount = a.Apartment_complex.Count()
}).ToArray();
}

I think you miss group by clause in your query.
or you can use corolated sub query in select clause. please explain your question more

how to convert this T-SQL statment to linq

i'm starter in linq, i have write this T-SQL Query
select * from DOCUMENT_TYPES where document_id in(
select document_id from Clearance_Document where Clearance_id=(select clearance_id from clearance_id from request where request_id=3))
i want convert this T-SQL Query to linq, please help me, thanks

Well, I would start first by refactoring your SQL into something other than a chain of nested sub-queries. I think this ought to do the same thing, and it's much more readable:
SELECT
*
FROM
DOCUMENT_TYPES dt
JOIN
Clearance_Document cd
ON
dt.document_id = cd.document_id
JOIN
Request r
ON
cd.clearance_id = r.clearance_id
WHERE
r.request_id = 3
(I'm assuming that from clearance_id from request was a typo.)
Then you can easily refactor into a LINQ statement:
var result = from dt in DOCUMENT_TYPES
join cd in Clearance_Document on dt.document_id equals cd.document_id
join r in Request on cd.clearance_id equals r.clearance_id
where r.request_id = 3
select new {
property1 = dt.something,
property2 = cd.somethingElse,
...
};

var result =
from a in DOCUMENT_TYPES
let list =
(
from b in Clearance_Document
where b.Clearance_id == (from c in clearance_id where request_id == 3).First<string>())
select b
).ToList()
where list.Contains(a.document_id)
select a;

Something like that should do (i guessed you're using EF, but you can easyly adapt to other LinQ-Types):
context.Document_Types.Where(doc =>
conext.Clearance_Document.Where(cd =>
cd.Clearance_Id == context.Request.Single(r => r.Request_Id == 3)
).Contains(doc.Document_Id)
).ToList();

How about
var result = c.Id context.Request.Single(r => r.Id == 3)
.Clearances.SelectMany(c => x.DocumentTypes);
In effect, get the one and only Request with an Id equal to 3, then get all the DocumentTypes of all its Clearances.
If your database is set up with the appropriate foreign keys these relationships will be automatically generated as part of your model.

How to rewrite a SQL query in LINQ to Entities?

I'm trying to rewrite a SQL query in LINQ to Entities. I'm using LINQPad with a typed datacontext from my own assembly to test things out.
The SQL query I'm trying to rewrite:
SELECT DISTINCT variantID AS setID, option_value AS name, option_value_description AS description, sort_order as sortOrder
FROM all_products_option_names AS lst
WHERE lst.optionID=14 AND lst.productID IN (SELECT productID FROM all_products_option_names
WHERE optionID=7 AND option_value IN (SELECT name FROM brands
WHERE brandID=1))
ORDER BY sortOrder;
The LINQ to Entities query I've come up with so far (which doesn't work due to a timeout error):
from a in all_products_option_names
where a.optionID == 14 && all_products_option_names.Any(x => x.productID == a.productID && x.optionID == 7 && brands.Any(y => y.name == x.option_value && y.brandID == 1))
select new
{
id = a.variantID,
name = a.option_value,
description = a.option_value_description,
sortOrder = a.sort_order,
}
This is the error I get when I run the above query: An error occurred while executing the command definition. See the inner exception for details.
And the inner exception is: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
Edit:
I use MySQL and probably that's why LINQPad doesn't show me the generated SQL.
The SQL version doesn't time out.
Edit 2:
I solved the problem by completely changing the query, so this question is irrelevant now.
I marked Steven's response as the correct one, because he was closest to what i was trying to achieve and his response gave me the idea which led me to the solution.

Try this:
var brandNames =
from brand in db.Brands
where brand.ID == 1
select name;
var brandProductNames =
from p in db.all_products_option_names
where p.optionID == 7
where brandNames.Contains(p.option_value)
select p.productId;
var results =
from p in db.all_products_option_names
where p.optionID == 14
where brandProductNames.Contains(p.productId)
select new
{
setID = p.variantID,
name = p.option_value,
description = p.option_value_description,
sortOrder = p.sort_order
};

I would recommend doing joins rather than sub-select's as you have them. Sub-selects are not very efficient when you look at performance, it's like having loops inside of loops when you code , not a good idea. This could actually cause that timeout your getting if your database is running slowly even thou that looks like a simple query.

I would try using joins with a distinct at the end like this:
var results =
(from p in db.all_products_option_names
join p2 in db.all_products_option_names on p.productId equals p2.productId
join b in db.Brands on p2.option_value equals b.name
where p.optionID == 14
where p2.optionID == 7
where b.BrandID == 1
select new
{
setID = p.variantID,
name = p.option_value,
description = p.option_value_description,
sortOrder = p.sort_order
}).Distinct();
Or you could try using joins with the into and with an any like so
var results =
from p in db.all_products_option_names
join p2 in (from p3 in db.all_products_option_names.Where(x => x.optionId == 7)
join b in db.Brands.Where(x => x.BrandID == 1) on p3.option_value equals b.name
select p3) into pg
where p.optionID == 14
where pg.Any()
select new
{
setID = p.variantID,
name = p.option_value,
description = p.option_value_description,
sortOrder = p.sort_order
};