I am having trouble figuring out how (and where) to order a subcollection in a LINQ/EF query.
Basically I have a collection of SubscriptionTypes, each having its own collection of Subscriptions. I would like each Subscription in the collection to be ordered by NumberOfMonths.
Here is my current query:
public IQueryable<SubscriptionType> SubscriptionTypesByProperty(string propertyCode)
{
return from a in db.SubscriptionTypes.Include("Subscriptions")
where a.Subscriptions.Any(x => x.PropertyCode == propertyCode)
select a;
}
I would like the Subscriptions to be ordered by NumberOfMonths. I tried this:
public IQueryable<SubscriptionType> SubscriptionTypesByProperty(string propertyCode)
{
return from a in db.SubscriptionTypes.Include("Subscriptions")
where a.Subscriptions.OrderBy(q => q.NumberOfMonths).Any(x => x.PropertyCode == propertyCode)
select a;
}
.. but that did not order the subscriptions correctly.
Does anybody know of an easy way to do this?
UPDATE: SubscriptionType and Subscription are types generated by the EF designer.
Thanks,
Adam
Change your select part to sth like this
select new SubscriptionType{ ?,?,?,
Subscriptions = a.Subscription.OrderBy(b=>b.?)}
You can change your existing query to this, and it should do what you're looking for.
public IQueryable<SubscriptionType> SubscriptionTypesByProperty(string propertyCode)
{
return from a in db.SubscriptionTypes.Include("Subscriptions")
where a.Subscriptions.Any(x => x.PropertyCode == propertyCode)
order by a.NumberOfMonths descending
select a;
}
Obviously, descending could be ascending if that's what you want.
Related
I have the following domain classes
class EventA {
static belongsTo = [offer: Offer]
}
class EventB extends EventA {}
class EventC extends EventA {}
class Offer {
static hasMany [events: EventA]
}
I need to retrieve offers that are not associated with an EventC.
In SQL this can easily be performed as:
SELECT *
FROM OFFER O
LEFT JOIN EVENTC C ON O.event_id = C.id
WHERE C.ID IS NULL
Searching through the grails documentation I found instanceOf. Stating that once you have the result set you can perform a check of the instance type.
def offers = Offer.list()
for (Offer o in offers) {
for(Event e : o.events) {
if (e.instanceOf(EventC)) {
// no bueno
}
}
}
The above just feels wrong. I would prefer to have the database do such filtering for me. Is there a way to perform such a filter with searchCriteria?
You can accomplish this by querying the Event classes directly. That way you can specifically query the flavor of Event you care about. Then query the Offer table with the list of Id's
Offer.findAllByIdInList(EventC.list().offerId)
This actually ended up being easier then I expected. On my search criteria, I can build an expression to not include any Offer that has an event EventC.
Example:
Offer.with {
events {
ne('class', EventC)
}
}
Since I questioned this approach I enabled hibernate logging. Ironically, it generated SQL that was pretty similar to what I was after.
SELECT *
FROM OFFER O
LEFT JOIN EVENTB B ON O.ID == B.EVENT_ID
LEFT JOIN EVENTC C ON O.ID == C.EVENT_ID
WHERE
(
CASE
WHEN B.ID IS NOT NULL THEN 1
WHEN C.ID IS NOT NULL THEN 2
END <> ?
)
Lets Say a domain class A has many Class B objects. I need to do a criteria query which returns
A.id
A.name
B.count(no of B elements associated with A)
B.last Updated(date of most recent update of B elements associated with A considering i have last_updated date for all B elements)
Also the query should be flexible enough to add conditions/restrictions to both A and B domain objects.
Currently I have gotten as far as this:
A.createCriteria().list {
createAlias('b','b')
projections{
property('id')
property('gender')
property('dateOfBirth')
count('b.id')
property('publicId')
}
}
But the problem is that it only returns one object and the count of child objects is for all the elements of B instead of just those associated with A
Recently I was in a similar scenario I needed a query in which one of your rows will store the count of many in a one-to-many relationship
But unlike your scenario I used native sql queries to resolve the query.
The solution was to use derived tables (I do not know how to implement them using criteria query).
In case you find it useful I share a code with the implementation taken from a grails service:
List<Map> resumeInMonth(final String monthName) {
final session = sessionFactory.currentSession
final String query = """
SELECT
t.id AS id,
e.full_name AS fullName,
t.subject AS issue,
CASE t.status
WHEN 'open' THEN 'open'
WHEN 'pending' THEN 'In progress'
WHEN 'closed' THEN 'closed'
END AS status,
CASE t.scheduled
WHEN TRUE THEN 'scheduled'
WHEN FALSE THEN 'non-scheduled'
END AS scheduled,
ifnull(d.name, '') AS device,
DATE(t.date_created) AS dateCreated,
DATE(t.last_updated) AS lastUpdated,
IFNULL(total_tasks, 0) AS tasks
FROM
tickets t
INNER JOIN
employees e ON t.employee_id = e.id
LEFT JOIN
devices d ON d.id = t.device_id
LEFT JOIN
(SELECT
ticket_id, COUNT(1) AS total_tasks
FROM
tasks
GROUP BY ticket_id) ta ON t.id = ta.ticket_id
WHERE
MONTHNAME(t.date_created) = :monthName
ORDER BY dateCreated DESC"""
final sqlQuery = session.createSQLQuery(query)
final results = sqlQuery.with {
resultTransformer = AliasToEntityMapResultTransformer.INSTANCE
setString('monthName', monthName)
list()
}
results
}
The part of interest is to declare a row within the main select and then in the clause from declare the derived query that stores the result in a row with the same name declared in the main select
SELECT ...
total_tasks --Add the count column to your select
FROM ticket t
JOIN (SELECT ticked_id, COUNT(1) as total_tasks
FROM tasks
GROUP BY ticked_id) ta ON t.id = ta.ticked_id
...rest of query
This last example I share from the answer made by the user Aaron Dietz to the question that I also formulate
I hope it is useful for you
Turns out I wasn't very far from the solution and i just needed to do grouping based on the right property which is the foreign key column in the child table which is b.a in this case so the following works now
A.createCriteria().list {
createAlias('b','b')
projections{
property('id')
property('gender')
property('dateOfBirth')
count('b.id')
groupProperty('b.a')
property('publicId')
}
}
In the criteria you need to group by the property which are not aggregate.
Try following:
A.createCriteria().list {
createAlias('b','b')
projections{
groupProperty('id','id')
groupProperty('gender','gender')
groupProperty('dateOfBirth','dateOfBirth')
count('b.id','total')
groupProperty('publicId','publicId')
}
}
or If you want to have a list of map object return you can try add resultTransformer(CriteriaSpecification.ALIAS_TO_ENTITY_MAP)
A.createCriteria().list {
resultTransformer(CriteriaSpecification.ALIAS_TO_ENTITY_MAP)
createAlias('b','b')
projections{
groupProperty('id','id')
groupProperty('gender','gender')
groupProperty('dateOfBirth','dateOfBirth')
count('b.id','total')
groupProperty('publicId','publicId')
}
}
Hope it can help
I'm trying to write a search function that will search trough the whole table and I'll get all columns, so far I'm using this code and I can only extract one column from the table, how can I get all columns.
CODE:
public ActionResult SearchIndex(string productsAll, string searchString)
{
var products = from m in db.Products
select m;
if (!String.IsNullOrEmpty(searchString))
{
products = products.Where(n => n.Name.Contains(searchString));
}
if (string.IsNullOrEmpty(productsAll))
return View(products);
else
{
return View(products);
}
}
Please HELP :D
You can filter based upon other columns as well...
products = products.Where(n => n.Name.Contains(searchString) ||
n.Prop2.Contains(searchString) ||
n.Prop3.Contains(searchString));
Which will get you any record which contains that string in any of the fields you specified.
I am trying to write a query that includes 2 joins.
1 StoryTemplate can have multiple Stories
1 Story can have multiple StoryDrafts
I am starting the query on the StoryDrafts object because that is where it's linked to the UserId.
I don't have a reference from the StoryDrafts object directly to the StoryTemplates object. How would I build this query properly?
public JsonResult Index(int userId)
{
return Json(
db.StoryDrafts
.Include("Story")
.Include("StoryTemplate")
.Where(d => d.UserId == userId)
,JsonRequestBehavior.AllowGet);
}
Thank you for any help.
Try to flatten your hierarchy if it works for you. Here is a sample, and you may want to customize it for your needs.
var result = from c in db.Customers
join o in db.Orders
on c equals o.Customers
select new
{
custid = c.CustomerID,
cname = c.CompanyName,
address = c.Address,
orderid = o.OrderID,
freight = o.Freight,
orderdate = o.OrderDate
};
If flattering does not meet your requirements then you need to use query that returns a Nested Group. Finally, look at the following link for more references - LINQ Query Expressions .
Given a table of order items (OrderItems) that relates to a table of orders (Orders), which in turn relates to a table of users (Users), is it possible to retrieve all the OrderItems and group them into a dictionary by OrderId with just one query? ie. without performing an iteration over either the OrderItems result set or performing a query for each order.
Desired controller pseudo-code
Dictionary<int,IEnumerable<OrderItem>> OrderItems = DataContext.OrderItems.ToDictionary(Key => oi.OrderId, Value => oi.ToList());
Desired usage:
IEnumerable<OrderItem> currentOrderItems = OrderItems[123]; // where 123 is OrderId
Current Method
In my Controller I presently retrieve a user's orders and order items to pass to the Orders view:
ViewData["Orders"] = (from o in orders
where o.UserId equals CurrentUserId
orderby o.DateCreated descending)
.ToList();
ViewData["OrderItems"] = (from oi in DataContext.OrderItems
join o in DataContext.Orders
on oi.OrderId equals o.OrderId
where o.UserId equals CurrentUserId
select oi)
.ToList();
Then in my view, I retrieve all order items:
IEnumerable<OrderItem> orderItems = ViewData["OrderItems"] as IEnumerable<OrderItem>;
and use LINQ to group and display each order's order items:
IEnumerable<OrderItem> currentOrderItems = orderItems.Where(
i => i.OrderId == order.OrderId
);
This is fairly efficient as only two queries are passed to the database and some processing is done in the view. But ideally, this should be done in the controller.
Solved it! With ToLookup(...)
ViewData["OrderItems"] = (from oi in DataContext.OrderItems
join o in DataContext.Orders
on oi.OrderId equals o.OrderId
where o.UserId == UserId
select oi).ToLookup(oi => oi.OrderId, oi => oi);
And in my view:
ILookup<int,OrderItem> orderItems = ViewData["OrderItems"] as ILookup<int,OrderItem>;
foreach (Order order in orders)
{
DisplayOrder(order);
// Now display this order's items:
foreach(OrderItem item in orderItems[order.OrderId])
{
DisplayOrderItem(item);
}
}
A trace shows only one query to create the lookup.
Looks like I'm making a habit out of answering my own questions...
I think your best bet is to create a method that accepts a lambda for the key and a list to be inserted into the dictionary and then simply enumerates the list and adds to the dictionary using the key provided in the lambda. The method could be an Extension Method of IDictionary and let's call it say, AddRangeWithKeyType()