If I do this...
Context.Orders.Select(o => o.User.UserId);
... I get an exception because User is null. I can use Include instead,
Context.Orders.Include(o => o.User).Select(o => o.User.UserId);
... but shouldn't User be loaded automatically?
EDIT:
The first snippet of code doesn't work when the Select is applied to the result of a function. Which type should the function return in order to tack the Select onto the database query?
I've tried IEnumerable<Order> and IQueryable<Order>.
Related
As I understand it, the following code should generate a query containing only the RouteId, RouteNo, and ShipId
var tow = (from t in _context.AllTowData
where t.RouteId == id
orderby t.RouteNo descending
select new TowDefaults {
Id = t.RouteId,
TowNo = t.RouteNo,
ShipId = t.ShipId,
LastTow = t.RouteNo
})
.FirstOrDefault();
However, I get:
SELECT v.route_id, v.route_no, v.tow_id, v.analysis_complete, v.checks_complete, v.cpr_id, v.date_created, v.date_last_modified, v.factor, v.fromportname, v.instrument_data_file, v.instrument_id, v.internal_number, v.mastername, v.message, v.miles_per_division, v.month, v.number_of_samples, v.number_of_samples_analysed_fully, v.prop_setting, v.route_status, v.sampled_mileage, v.serial_no_per_calendar_month, v.ship_speed, v.silk_reading_end, v.silk_reading_start, v.toportname, v.tow_mileage, v.validity, v.year
FROM view_all_tow_data AS v
WHERE v.route_id = '#__id_0'
ORDER BY v.route_no DESC
LIMIT 1
That's every column except the explicitly requested ShipId! What am I doing wrong?
This happens using both a SQL Server and a PostGres database
The property ShipIdis not mapped, either by a [NotMapped] annotation or a mapping instruction. As far as EF is concerned, the property doesn't exist. This has two effects:
EF "notices" that there's an unknown part the final Select and it switches to client-side evaluation (because it's a final Select). Which means: it translates the query before the Select into SQL which doesn't contain the ShipId column, executes it, and materializes full AllTowData entities.
It evaluates the Select client-side and returns the requested TowDefaults objects in which ShipId has its default value, or any value you initialize in C# code, but nothing from the database.
You can verify this by checking _context.AllTowData.Local after the query: it will contain all AllTowData entities that pass the filter.
From your question it's impossible to tell what you should do. Maybe you can map the property to a column in the view. If not, you should remove it from the LINQ query. Using it in LINQ anywhere but in a final Select will cause a runtime exception.
I am trying to insert a vertex with orientjs(previously oriento) query builder. My class has a link type property pointing to another class.
I know I can get it to work with a raw query string but I would love to use the query builder.
Here is what I've tried so far :
db.insert()
.into('VertexClassName')
.set({"prop":"value", "linkProperty":"33:1289287"})
db.insert()
.into('VertexClassName')
.set({"prop":"value", "linkProperty":"#33:1289287"})
I get the following error :
Error on saving record in cluster #13
Am I setting properties in the right way ?
Could the error be related to somtehing else ?
I have sucessfully ran an insert query in the cluster #13 with a raw query string in the studio...
According to the official documentation it seems that the problem might be at the end of your statement
db.insert().into('VertexClassName')
.set({"prop":"value", "linkProperty":"33:1289287"}).one()
.then(function (data) {
// callback
});
Check if your code works adding one() to the pipe line
EDITED: I found this method in orientjs.
db.create('VERTEX', 'V')
.set({
key: 'value',
foo: 'bar'
})
.one()
.then(function (vertex) {
console.log('created vertex', vertex);
});
When using Tinkerpop API they recommend using createVertex instead of insert, because createVertex is intended for graphs and insert for Documents... Could you try with the create() method instead?
I am using SQL and it worked.
sql = "INSERT INTO Station set linked = (select from LinkedClass where LinkedProb = 'value'), prop = 'value'"
OrientVertex vertex = new OrientVertex();
vertex = graph.command(new OCommandSQL(sql)).execute();
I don't think that's possible unless you've added a proper field with the right type 'Link' in your schema. (which I rarely do).
Now instead of having the right 'link' type inserted you can do the opposite, store is as a String, and leverage the query functions to use it correctly:
db.insert().into('table').set({prop: '#15:14'}).one();
And it will be converted as String (which is a bit sad) but then you can use that in your queries:
SELECT eval(prop) FROM table;
And it will be 'eval'-ed to a Node RecordID that you can directly use and call functions like expand() on.
For example:
SELECT name FROM (SELECT expand(eval(prop)) FROM table);
Will eval the node stored in the insert(), grab the node, expand it and collect its name property.
I have two tables in my database and one of the tables is associated with my Accounts table.
So in my Schema Result for Account.pm I added the following line.
__PACKAGE__->has_many('subjects', 'MyApp::DBIC::Schema::Subject', {'foreight.account_id' => 'self.account_id'});
Then in my controller I make a search like this.
$c->stash->{search_results} = $c->model('DB::Account')->search(
{ -or => [
firstname => {like => '%'.$search_term.'%'},
'subjects.subject_title' => {like => '%'.$search_term.'%'},
]
},
{
join => 'subjects',
rows => '3',
},
{
order_by => 'first name ASC',
page => 1,
rows => 10,
}
);
It does not output any errors, but I can't figure out how to output the results on my view file. Is this a correct method of making relations between two tables?
My goal: provided a search_term, search two tables and output the result in view file. My SQL would look something like this:
SELECT FROM Accounts,Subjects WHERE Accounts.firstname=$search_term OR Subjects.subject_title=$search_term LEFT JOIN Subjects ON Accounts.account_id=Subject.account_id
And would want to output the result in view file, as I stated above.
I am fairly new to Perl and some of the documentations don't make that much sense to me, still. So any help and tips are appreciated.
The join looks OK to me, but it would make sense to try a simplified version without the join to check that everything else is OK.
The behaviour of DBIx::Class::ResultSet::search differs depending on the context in which it's called. If it's called in list context then it executes the database query and returns an array of MyApp::DBIC::Schema::Account objects. For example:
my #accounts = $c->model('DB::Account')->search();
In your case you're calling search in scalar context, which means that rather than returning an array it will return a DBIx::Class::ResultSet object (or a subclass thereof), and crucially it won't actually execute a db query. For that to happen you need to call the all method on your resultset. So, assuming you're using the default template toolkit view you probably want something like this:
[% FOREACH search_result IN search_results.all %]
[% search_result.first_name %]
[% END %]
This 'lazy' behaviour of DBIx::Class is actually very useful, and in my opinion somewhat undersold in the documentation. It means you can keep a resultset in a variable and keep executing different search calls on it without actually hitting the DB, it can allow much nicer code in cases where you want to conditionally build up a complex query. See the DBIx::Class::Resultset documentation for further details.
You have error in your query:
Try:
$c->stash->{search_results} = $c->model('DB::Account')->search(
{ -or => [
firstname => {like => '%'.$search_term.'%'},
'subjects.subject_title' => {like => '%'.$search_term.'%'},
]
},
{
join => 'subjects',
order_by => 'firstname ASC',
page => 1,
rows => 10,
}
);
I am using Entity Framework 5.0 and I wish to return a list of objects, however, I want to perform a DISTINCT on one of the properties on each object within the list.
I know there are a few questions similar to mine already on Stackoverflow, however, I am still struggling with this one.
Currently my query looks like this
public IList<tblcours> GetAllCoursesByOrgID(int id)
{
return _UoW.tblcoursRepo.All.Where(c => c.tblCourseCategoryLinks.Any(cl => cl.tblUnitCategory.tblUnit.ParentID == id))
.OrderBy(c => c.CourseTitle)
.ToList();
}
However, I need to perform a DISTINCT on the property MainHeadingID to remove any objects already with the same ID, but still returning the entire object with all its properties.
Preferably, I would like to return IList, as you can see from my method, and not an Anonymous Type.
Any help with this is greatly appreciated.
Thanks.
Have you tried using GroupBy?
_UoW.tblcoursRepo.All.GroupBy(c => c.MainHeadingId)
.Select(g => g.FirstOrDefault())
Is there a way to use FirstOrDefault() inside a complex query but not throw an exception if it returns null value?
My query:
contex.Table1.Where(t => t.Property == "Value").FirstOrDefault()
.Object.Table2.Where(t => t.Property2 == "Value2").FirstOrDefault();
If the query on the first table (Table1) doesn't return an object the code throws an exception. Is there a way to make it return just null?
Try a SelectMany on Table2, without the intermediate FirstOrDefault():
context.Table1.Where(t1 => t1.Property1 == "Value1")
.SelectMany(t1 => t1.Table2.Where(t2 => t2.Property2 == "Value2"))
.FirstOrDefault();
Also, you might want to use SQL Profiler to check the SQL that is being sent by EF. I believe the query as constructed in your question will result in two queries being sent to the database; one for each FirstOrDefault().
You could build your own helper function, that takes IEnumerable
public static TSource CustomFirstOrDefault<TSource>(this IEnumerable<TSource> source)
{
return source.FirstOrDefault() ?? new List<TSource>();
}
This would effectively return an empty list, which, when called upon, providing your code in your Object property can handle nulls, won't bomb out, cause you'll just be returning a 0 item collection, instead of a null.
Only the first query with Where is a database query. As soon as you apply a "greedy" operator like FirstOrDefault the query gets executed. The second query is performed in memory. If Object.Table2 is a collection (which it apparently is) and you don't have lazy loading enabled your code will crash because the collection is null. If you have lazy loading enabled a second query is silently executed to load the collection - the complete collection and the filter is executed in memory.
You query should instead look like #adrift's code which would really be only one database query.