I'm attemping to do a simple check for an empty collection in an NHIbernate Query. Here's my code:
var query = QueryNotDeleted().Where(x=>x.Markets.Count() > 0);
QueryNotDeleted returns an IQueryOver. The above line throws an error (Unrecognised method call in epression x.Markets.Count()) because it doesn't recognize the Count() in the query.
I tried
var query = QueryNotDeleted().Where(x=>x.Markets != null);
But unfortunately, Markets is never NULL, so I have to test for a count instead of it being null to get the records I want.
How can I get this "count" syntax correct so that it excludes records where the Markets property is empty?
I was able to get it to work using:
query.RootCriteria.CreateAlias("Markets", "m", JoinType.LeftOuterJoin);
and then
query.RootCriteria.Add(Restrictions.IsNotNull("m.Id"));
If I understand your question correctly you want to get a list of records that don't have corresponding children?
If I wanted to get a list of Orders that have no OrderItems using QueryOver then I would do something like:-
var orders = session.QueryOver<Order>()
.Left.JoinQueryOver(w => w.Items)
.Where(w => w.Order.Id == null);
If this is not the right answer then please can you submit the SQL you are trying to run and the parent/children mappings/.
Related
I am wondering how I can use where cause with the ActiveRecord find method.
Here is the code I am using:
Supplier.joins(:products).find(params[:id]).where('suppliers.permalink = ? AND variants.master = ?', params[:id], TRUE)
which gives me:
undefined method `where' for #<Supplier:0x007fe49b4eb330>
Supplier.joins(:products).find(params[:id]).where('suppliers.permalink = ? AND variants.master = ?', params[:id], TRUE)
What you're doing here is finding the first record with the id contained in params[:id], then trying to run a where statement on that single record. where only works when run against the model itself.
The confusing part here is that you are using params[:id] both for the primary key (find searches the id field) but then also comparing it to the permalink column in the where clause.
To explain the usage of both methods:
find will search for result(s) from the table, matching the argument you provide it to the id field. You can pass in multiple id's and this method is mostly used to select a row that you know exists, by id. Most commonly it is used with a single id and returns a single instance.
where is used to find all results from the table that match the clause and return a collection of records. You can then refine these results or select one, for example by using .first:
Supplier.joins(:products).where('suppliers.permalink = ? AND variants.master = ?', params[:permalink], true).first
(Note that you're using joins(:products) but then querying variants table. Is this incorrect?)
Supplier.joins(:products).where('suppliers.permalink = ? AND variants.master = ?', params[:id], TRUE).find(params[:id])
I need some help in building the correct query. I have an Employees table. I need to get a list of all employees, that EENO (Employee ID) contains a string from a supplied array of partial Employee IDs.
When I use this code
// IEnumerable<string> employeeIds is a collection of partial Employee IDs
IQueryable<Employee> query = Employees;
foreach (string id in employeeIds)
{
query = query.Where(e => e.EENO.Contains(id));
}
return query;
I will get something like:
SELECT *
FROM Employees
WHERE EENO LIKE '%1111111%'
AND EENO LIKE '%2222222%'
AND EENO LIKE '%3333333%'
AND EENO LIKE '%4444444%'
Which doesn't make sense.
I need "OR" instead of "AND" in resulting SQL.
Thank you!
UPDATE
This code I wrote using PredicateBuilder works perfectly when I need to include these employees.
var predicate = PredicateBuilder.False<Employee>();
foreach (string id in employeeIds)
{
var temp = id;
predicate = predicate.Or(e => e.EENO.Contains(temp));
}
var query = Employees.Where(predicate);
Now, I need to write an opposite code, to exclude these employees,
here it is but it is not working: the generated SQL is totally weird.
var predicate = PredicateBuilder.False<Employee>();
foreach (string id in employeeIds)
{
var temp = id;
predicate = predicate.And(e => !e.EENO.Contains(temp)); // changed to "And" and "!"
}
var query = Employees.Where(predicate);
return query;
It's supposed to generate SQL Where clause like this one:
WHERE EENO NOT LIKE '%11111%'
AND NOT LIKE '%22222%'
AND NOT LIKE '%33333%'
But it's not happening
The SQL generated is this: http://i.imgur.com/9MDP7.png
Any help is appreciated. Thanks.
Instead of the foreach, just build the IQueryable once:
query = query.Where(e => employeeIds.Contains(e.EENO));
I'd take a look at http://www.albahari.com/nutshell/predicatebuilder.aspx. This has a great way of building Or queries, and is written by the guy that wrote LinqPad. The above link also has examples of usage.
I believe you can use Any():
var query = Employees.Where(emp => employeeIds.Any(id => id.Contains(emp.EENO)));
If you don't want to use a predicate builder, then the only other option is to UNION each of the collections together on an intermediate query:
// IEnumerable<string> employeeIds is a collection of partial Employee IDs
IQueryable<Employee> query = Enumerable.Empty<Employee>().AsQueryable();
foreach (string id in employeeIds)
{
string tempID = id;
query = query.Union(Employees.Where(e => e.EENO.Contains(tempID));
}
return query;
Also keep in mind that closure rules are going to break your predicate and only end up filtering on your last criteria. That's why I have the tempID variable inside the foreach loop.
EDIT: So here's the compendium of all the issues you've run across:
Generate ORs instead of ANDS
Done, using PredicateBuilder.
Only last predicate is being applied
Addressed by assigning a temp variable in your inner loop (due to closure rules)
Exclusion predicates not working
You need to start with the correct base case. When you use ORs, you need to make sure you start with the false case first, that way you only include records where AT LEAST ONE predicate matches (otherwise doesn't return anything). The reason for this is that the base case should just get ignored for purposes of evaluation. In other words false || predicate1 || predicate2 || ... really is just predicate1 || predicate2 || ... because you're looking for at least one true in your list of predicates (and you just need a base to build on). The opposite applies to the AND case. You start with true so that it gets "ignored" for purposes of evaluation, but you still need a base case. In other words: true && predicate1 && ... is the same as predicate1 && .... Hope that addresses your last issue.
I am trying to filter only negative values using nhibernate projection queries. Below is my code for it
SearchTemplate RefundTemplate = new SearchTemplate();
RefundTemplate.Criteria = DetachedCriteria.For(typeof(AirBilling), "Ab");
RefundTemplate.Criteria.Add(NHibernate.Criterion.Expression.Eq("PaymentType", "CK"));
RefundTemplate.Criteria.Add(NHibernate.Criterion.Restrictions.Lt("Gross",0));
Basically I am tying to get all the records from the AirBilling table that have a PaymentType CK and Gross value is less that zero. But somehow the code doesnt work. It doesnt throw any errors, but it simply wont work.
It could be because you are giving your entity an alias ("Ab"), so when you reference the properties you need to prefix them with the alias, eg: Expression.Eq("Ab.PaymentType", "CK")
try this:
SearchTemplate RefundTemplate = new SearchTemplate();
RefundTemplate.Criteria = DetachedCriteria.For(typeof(AirBilling), "Ab");
RefundTemplate.Criteria.Add(NHibernate.Criterion.Expression.Eq("Ab.PaymentType", "CK"));
RefundTemplate.Criteria.Add(NHibernate.Criterion.Restrictions.Lt("Ab.Gross",0));
I am stuck with a problem here. I am trying to compare items in a list to another list with much more items using linq.
For example:
list 1: 10,15,20
list 2: 10,13,14,15,20,30,45,54,67,87
I should get TRUE if all the items in list 1 occur in list 2. So the example above should return TRUE
Like you can see I can't use sequenceEquals
Any ideas?
EDIT:
list2 is actually not a list it is a column in sql thas has following values:
<id>673</id><id>698</id><id>735</id><id>1118</id><id>1120</id><id>25353</id>.
in linq I did the following queries thanks to Jon Skeets help:
var query = from e in db
where e.taxonomy_parent_id == 722
select e.taxonomy_item_id;
query is IQueryable of longs at this moment
var query2 = from e in db
where query.Contains(e.taxonomy_item_id)
where !lsTaxIDstring.Except(e.taxonomy_ids.Replace("<id>", "")
.Replace("</id>", "")
.Split(',').ToList())
.Any()
select e.taxonomy_item_id;
But now I am getting the error Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
How about:
if (!list1.Except(list2).Any())
That's about the simplest approach I can think of. You could explicitly create sets etc if you want:
HashSet<int> set2 = new HashSet<int>(list2);
if (!list1.Any(x => set2.Contains(x)))
but I'd expect that to pretty much be the implementation of Except anyway.
This should be what you want:
!list1.Except(list2).Any()
var result = list1.All(i => list2.Any(i2 => i2 == i));
I need to get maximum page order from database:
int maxOrder = GetSession.Query<Page>().Max(x => x.PageOrder);
The above works if there are rows in the database table, but when table is empty I'm getting:
Value cannot be null.
Parameter name: item
In the way you are doing it is normal to get an exception as the enumerable, that the GetSession.Query<Page>() returns, is empty (because the table is empty as you mentioned).
The exception that you should be getting is: Sequence contains no elements.
The exception you mention in your question is because the item variable (which is irrelevant with the NHiberanate query you list above) is null (line 54 assigns the item property to null).
A safer way to get the max from a property in a table would be the following:
var max = GetSession.CreateCriteria<Page>()
.SetProjection(Projections.Max("PageOrder"))
.UniqueResult();
or using QueryOver with NHibenrate 3.0:
var max = GetSession.QueryOver<Page>()
.Select(
Projections
.ProjectionList()
.Add(Projections.Max<Page>(x => x.PageOrder)))
.List<int>().First();
If the table is empty you will get max = 0
Session.Query<Page>().Max(x => (int?)x.PageOrder)
Note the cast (I'm assuming PageOrder is an int)
If you are having problems with the QueryOver example by tolism7 (InvalidCastException), here's how I got it working:
var max = session.QueryOver<Page>()
.Select(Projections.Max<Page>(x => x.PageOrder))
.SingleOrDefault<object>();
return max == null ? 0 : Convert.ToInt32(max);