I have this linq query
Dim chiamateAperte = From statoRic In
dbVulcano.StatoRic.Where(Function(s) s.RFStato >= 11 And s.RFStato <= 13 And s.Attuale = 1 And s.RFTecnico = rfTecnico)
From richiesta In
dbVulcano.Richieste.Where(Function(r) r.IDRic = statoRic.RFRic).DefaultIfEmpty()
From cliente In
dbVulcano.Clienti.Where(Function(c) c.IDCliente = richiesta.RFCliente).DefaultIfEmpty()
Select statoRic.ID, statoRic.RFRic, statoRic.RFStato, statoRic.Attuale, richiesta.Descr, cliente.RagSociale, statoRic.DataAss, statoRic.Data, dataf = If(statoRic.DataAss.HasValue, statoRic.DataAss, statoRic.Data), statoRic.OraDalle, statoRic.OraAlle
Order By dataf Descending, statoRic.OraDalle Ascending
It's working fine but I want to add an order condition on "OraDalle" field.
OraDalle it's sort of a time field, but sadly on db it's defined as smallInt (and I cannot change it), so the format is like "800" to say "eight o'clock". This field can be null.
So instead of statoRic.OraDalle I tried this:
orad=if (statoRic.OraDalle.HasValue,statoRic.OraDalle,2359)
And then
Order By dataf Descending, orad Ascending
But it throws an ugly error: cannot cast system nullable 1 to system object of type 'system.nullable'. Only primitive types or enumeration types are supported in this context
Then I tried this:
orad=statoRic.OraDalle.GetValueOrDefault(2359)
But it also throw an error like: linq to entities does not recognize the method 'Int16 GetValueOrDefault(Int16)'
So... how can I achieve what I want? This whole mess is to get a list ordered by time, where null time values are at the bottom (and not on the top, as default). Thank you all!
Instead of if (statoRic.OraDalle.HasValue,statoRic.OraDalle,2359) use if (statoRic.OraDalle,2359)
This is the equivalent of C#´s null-coalescing-operator ??:
statoRic.OraDalle ?? 2359 which was the solution for a similar question.
Related
Tired brain - perhaps you can help.
My table has two bit fields:
1) TestedByPCL and
2) TestedBySPC.
Both may = 1.
The user interface has two corresponding check boxes. In the code I convert the checks to int.
int TestedBySPC = SearchSPC ? 1 : 0;
int TestedByPCL = SearchPCL ? 1 : 0;
My WHERE clause looks something like this:
WHERE TestedByPCL = {TestedByPCL.ToString()} AND TestedBySPC = {TestedBySPC.ToString()}
The problem is when only one checkbox is selected I want to return rows having the corresponding field set to 1 or both fields set to 1.
Now when both fields are set to 1 my WHERE clause requires both check boxes to be checked instead of only one.
So, if one checkbox is ticked return records with with that field = 1 , regardless of whether the other field = 1.
Second attempt (I think I've got it now):
WHERE ((TestedByPCL = {chkTestedByPCL.IsChecked} AND TestedBySPC = {chkTestedBySPC.IsChecked})
OR
(TestedByPCL = 1 AND TestedBySPC = 1 AND 1 IN ({chkTestedByPCL.IsChecked}, {chkTestedBySPC.IsChecked})))
Misunderstood the question.
Change the AND to an OR:
WHERE TestedByPCL = {chkTestedByPCL.IsChecked} OR TestedBySPC = {chkTestedBySPC.IsChecked}
Also:
SQL Server does not have a Boolean data type, it's closest option is a bit data type.
The usage of curly brackets suggests using string concatenations to build your where clause. This might not be a big deal when you're handling checkboxes but it's a security risk when handling free text input as it's an open door for SQL injection attacks. Better use parameters whenever you can.
Good Day,
I am querying my database using Linq and I have run into a problem, the query searched a column for a search phrase and based on if the column has the phrase, it then returns the results, The query is below,
Dim pdb = New ProductDataContext()
Dim query =
From a In pdb.tblUSSeries
Join b In pdb.tblSizes_ On a.Series Equals b.Series
Where
a.Series.ToString().Equals(searchString) Or
b.Description.Contains(searchString) Or Not b.Description.Contains(Nothing)
Order By b.Series, b.OrderCode Ascending
Select New CustomSearch With
{
.Series = a.Series,
.SeriesDescription= a.Description,
.Coolant = a.Coolant,
.Material = a.Material,
.Standard = a.Standard,
.Surface = a.Surface,
.Type = a.Type,
.PointAngle = a.PointAngle,
.DiaRange = a.DiaRange,
.Shank = b.Shank,
.Flutes = b.Flutes,
.EDPNum = b.EDPNum,
.SizesDescription = b.Description,
.OrderCode = b.OrderCode
}
Return query
I think the problem is that, in the table certain rows are NULL, so when it is checking the column for the phrase and it encounters a row that is null it, breaks and returns this error,
The cast to value type 'System.Int32' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.
I have ran this query against another column that has all the rows populated with data and it returns the results ok.
So my question is how can I write it in VB to query the db with the supplied searchstring and return the results, when some of the rows in the columns have null values.
Any help would be great.
The exception occurs when you make the projection (i.e. select new CustomSearch)
And yes your trying to assign Null to some int property
(Not sure which one of your properties that is)
one of 2 choices :
1) Use nullalbe types for your properties (or just that one property).
2) project with an inline If ( ?? in C#) , I don't know VB so don't catch me on the syntax.
Taking Series just as an example i don't know if it's an int or if that's the problematic property
Select New CustomSearch With
{
.Series = If(a.Series Is Nothing,0, CInt(a.Series))
}
In C#
Select new CustomSearch
{
Series = a.Series ?? 0;
}
I am using VS2013 with SQL server 2012, VB.net. I am developing a web application.
Let me say before I ask the question that this will probably be extremely simple for this board but I have not been able to find this through googling.
I have an SQL table that holds some data, two columns (settingName (nvarchar) and settingValue (float)). I want to do the following but using LinQ.
SELECT Settingvalue
FROM Settings
WHERE settingName = 'Name1'
I have the following so far in VB.
Dim db As New GMConnectionDataContext
Dim result = From a In db.Settings
Where a.SettingName = "Name1"
Select a.SettingValue
txtEgdon.Text = result
This doesn't work as result is a double but if I add .tostring to result then the output in the text box is the full linq query not the result I am looing for.
I just need to understand this simple query so I can build on it but I just cant get it and any help offered would be great.
This is because your result is an IQueryable and not a single value(even if you expect it to be). This is also why ToString will get you the SQL that will be run against your DB.
You need to get either the First or if you are really sure this would be a single value get Single. The OrDefaults are used in the case that no value is returned so the result will be null.
A Few options:
// You expect 1 to many results and get the first
txtEgdon.Text = result.First().ToString()
// You expect 0 to many results and get the first or null in case of zero results
txtEgdon.Text = result.FirstOrDefault().ToString()
// You expect exactly 1 result and get it (you will get an exception if no results are returned)
txtEgdon.Text = result.Single().ToString()
// You expect exactly 0 or 1 results and get null or the result
txtEgdon.Text = result.SingleOrDefault().ToString()
I would prefer the FirstOrDefault()
I have a NHibernate search function where I receive integers and want to return results where at least the beginning coincides with the integers, e.g.
received integer: 729
returns: 729445, 7291 etc.
The database column is of type int, as is the property "Id" of Foo.
But
int id = 729;
var criteria = session.CreateCriteria(typeof(Foo))
criteria.Add(NHibernate.Criterion.Expression.InsensitiveLike("Id", id.ToString() + "%"));
return criteria.List<Foo>();
does result in an error (Could not convert parameter string to int32). Is there something wrong in the code, a work around, or other solution?
How about this:
int id = 729;
var criteria = session.CreateCriteria(typeof(Foo))
criteria.Add(Expression.Like(Projections.Cast(NHibernateUtil.String, Projections.Property("Id")), id.ToString(), MatchMode.Anywhere));
return criteria.List<Foo>();
Have you tried something like this:
int id = 729;
var criteria = session.CreateCriteria(typeof(Foo))
criteria.Add(NHibernate.Criterion.Expression.Like(Projections.SqlFunction("to_char", NHibernate.NHibernateUtil.String, Projections.Property("Id")), id.ToString() + "%"));
return criteria.List<Foo>();
The idea is convert the column before using a to_char function. Some databases do this automatically.
AFAIK, you'll need to store your integer as a string in the database if you want to use the built in NHibernate functionality for this (I would recommend this approach even without NHibernate - the minute you start doing 'like' searches you are dealing with a string, not a number - think US Zip Codes, etc...).
You could also do it mathematically in a database-specific function (or convert to a string as described in Thiago Azevedo's answer), but I imagine these options would be significantly slower, and also have potential to tie you to a specific database.
SQL query in Ms-Access
INSERT INTO tblTmpEventLog( TrackingNumber, PartNumber, PartNumberChgLvl,
EnteredBy, EventTypeSelected, EventDate )
SELECT DISTINCT tblRevRelLog_Detail.RevRelTrackingNumber,
tblRevRelLog_Detail.PartNumber, tblRevRelLog_Detail.ChangeLevel,
[Forms]![frmEventLog_Input]![EnteredBy] AS EnteredBy,
[Forms]![frmEventLog_Input]![EventTypeSelected] AS EventTypeSelected,
CDate([Forms]![frmEventLog_Input]![EventDate]) AS EventDate
FROM tblRevRelLog_Detail LEFT JOIN tblEventLog
ON (tblEventLog.PartNumber = tblRevRelLog_Detail.PartNumber)
AND (tblEventLog.PartNumberChgLvl = tblRevRelLog_Detail.ChangeLevel)
WHERE ((([tblRevRelLog_Detail]![RevRelTrackingNumber]) =
[Forms]![frmEventLog_Input]![TrackingNumber]))
AND ((tblEventLog.PartNumber) NOT IN
(SELECT tblEventLog.PartNumber FROM tblEventLog
WHERE tblEventLog.EventTypeSelected = 'pn REMOVED From Wrapper'
AND tblEventLog.TrackingNumber =
tblRevRelLog_Detail.RevRelTrackingNumber
AND tblEventLog.PartNumber = tblRevRelLog_Detail.PartNumber
AND tblEventLog.PartNumberChgLvl =
tblRevRelLog_Detail.ChangeLevel
));
DISTINCT keyword for EnteredBy, EventTypeSelected is not working..I mean, data for these columns is not displaying when I use DISTINCT keyword.
EVENTDATE is working fine, but I do not understand why is it not displaying for EneteredBy and EventTypeSelected columns.
Can anyone tell me how to handle this?
It may be that the query can't interpret properly from the form directly as the final data type. However in your date field, you are wrapping it in a function CDATE( ... ). So, the SQL engine knows the result type. I would suggest doing the same for the other fields. Ex: doing a CAST ( ...your form control... as DateTime ) as OtherColumn, etc... I THINK Access allows casting, but not positive. Otherwise, pre-pull the form value into a declared data type variable and use THAT variable in the query AS OtherColumn as you are doing.
Additionally to what #Jack mentioned, you can always go back to your account, look at your historical question, and click on whatever answers actually helped / solve your problems. Some questions never do get answers and that's ok, just give credit to those that DO help.
I have found in the past (I don't remember which old version of Access this was) that if you set the value of a form control in VBA, and then use that control in a query, the query will not see the value you set in VBA. If the user edits the control normally, the query sees the expected value. Perhaps that's what happened here.
To work around that, you can declare a VBA function that returns the desired value. For example, instead of this:
SELECT ..., Forms!MainForm!TextEntry AS TextEntry, ... FROM ...
use this:
SELECT ..., GetTextEntry() AS TextEntry, ... FROM ...
along with this:
Public Function TextEntry() As Variant
TextEntry = Forms!MainForm!TextEntry
End Function