I have a table that contains procedure codes among other data (let's call it "MyData"). I have another table that contains valid procedure codes, their descriptions, and the dates on which those codes are valid. Every time I want to report on MyData and include the procedure description, I have to do a lookup similar to this:
From m in dc.MyDatas _
Join p in dc.Procedures On m.proc_code Equals p.proc_code _
Where p.start_date <= m.event_date _
And If(p.end_date.HasValue, p.end_date.Value, Now) >= m.event_date _
Select m.proc_code, p.proc_desc
Since there are many places where I want to show the procedure description, this gets messy. I'd like to have the lookup defined in one place, so I tried putting this in an extension of MyData:
Partial Public Class MyData
Public ReadOnly Property ProcedureDescription() As String
Get
Dim dc As New MyDataContext
Return _
(From p in dc.Procedures _
Where p.proc_code = Me.proc_code _
And p.start_date <= Me.event_date _
And If(p.end_date.HasValue, p.end_date.Value, Now) >= Me.event_date _
Select p.proc_desc).SingleOrDefault
End Get
End Property
End Class
Which works when displaying data, but you can't use it in a query, because it doesn't know how to turn it into a SQL statement:
Dim test = _
From x In dc.MyDatas _
Select x.proc_code _
Where x.ProcedureDescription.Contains("test")
Error: The member 'MyProject.MyData.ProcedureDescription' has no supported translation to SQL.
Is there a way to turn a complex lookup (i.e. a non-trivial join) like this into something SQL can recognize so that I can define it in one place and just reference the description as if it were a field in MyData? So far the only thing I can think of is to create a SQL view on MyData that does the linking and bring that into my data context, but I'd like to try to avoid that. Any ideas would be welcomed. Thanks.
You can insert an AsEnumerable() into your query expression. That will convert everything to that point to a result set so that your custom properties can be included in the remainder of the expression (sorry I don't do VB):
var test = _
(from x in dc.MyDatas
(select x.proc_code).AsEnumerable().
Where(x => x.ProcedureDescription.Contains("test"));
this is not an extension method, it's a property
VB.net Extension methods: http://msdn.microsoft.com/en-us/library/bb384936.aspx
Consider using this query as a stored procedure if it's really important.
Related
After populating the recordsource the next action is clicking on one of the fields populated to "activate" the record. When clicking this, the goal is that the SEC_ID (A GUID, Number Data Type) is stored as a tempvar and used in future queries. This GUID is also placed in a text box just for a visual debug. However it doesn't put the GUID, it puts random Chinese characters. I've tried to place it into a MsgBox just to also see and it spits out "???????".
My code to populate the rowsource:
Dim componentListSQL As String
If FCSUtilities.AssessmentUoM = "Metric" Then
componentListSQL = "SELECT DISTINCT [100b_Working].SEC_SYS_COMP_ID, [100b_Working].SEC_ID, [110b_RO_Material_Category].MAT_CAT_DESC, [110b_RO_Component_Type].COMP_TYPE_DESC, [110b_RO_Material_Category].MAT_CAT_ID, [110b_RO_Component_Type].COMP_TYPE_ID, [100b_Working].ID_Number, [100b_Working].Model, [100b_Working].Serial_Number, [100b_Working].Capacity, [100b_Working].Manufacturer, [100b_Working].SEC_YEAR_BUILT, ROUND([100b_Working].SEC_QTY, 0) AS SEC_QTY, [100b_Working].UOM_MET_UNIT_ABBR, [100b_Working].UOM_ENG_UNIT_ABBR, [100b_Working].Equipment_Make, [100b_Working].UOM_CONV " _
& "FROM (110b_RO_Units_Conversion INNER JOIN (110b_RO_Component_Type INNER JOIN (110b_RO_Material_Category INNER JOIN 110b_RO_CMC ON [110b_RO_Material_Category].MAT_CAT_ID = [110b_RO_CMC].CMC_MCAT_LINK) ON [110b_RO_Component_Type].COMP_TYPE_ID = [110b_RO_CMC].CMC_CTYPE_LINK) ON [110b_RO_Units_Conversion].UOM_ID = [110b_RO_CMC].CMC_UoM) INNER JOIN 100b_Working ON [110b_RO_CMC].CMC_ID = [100b_Working].SEC_CMC_LINK " _
& "WHERE ((([100b_Working].SEC_SYS_COMP_ID) = [Forms]![200a_MainWindow]![txtDebugCompSysID]) And (([100b_Working].SEC_ID) Is Not Null)) " _
& "ORDER BY [110b_RO_Component_Type].COMP_TYPE_DESC;"
Me![210_ComponentList].Form.RecordSource = componentListSQL
End If
The OnClick event:
Private Sub txtMaterialCategory_Click()
Me.txtActiveSecID.Value = Me.txtSecID.Value
End Sub
The txtSecID appears as a GUID as it should but it's in the txtActiveSecID that it becomes Chinese characters even if I attempt to put it as a tempvar then set it into the txtActiveSecID.
I'm not exactly sure what is going on. Looking at different stacks, it points that it's due to long/memo field but as I said previously, the SEC_ID field data type is Number.
Per MS documentation https://learn.microsoft.com/en-us/office/vba/api/Access.Application.StringFromGUID:
The Microsoft Access database engine stores GUIDs as arrays of type Byte. However, Access can't return Byte data from a control on a form or report. To return the value of a GUID from a control, you must convert it to a string. To convert a GUID to a string, use the StringFromGUID function. To convert a string back to a GUID, use the GUIDFromString function.
StringFromGUID(Me.txtSecID.Value)
However that results in output like:
{guid {2786C27B-CB7C-4DEA-8340-1338532742DE}}
That should still work as filter critera but could do further processing to extract GUID from that string. Use string manipulation functions to remove the {guid header and trailing }. Review Access - GUID value stored in textbox, can't be used in SELECT statements
I've got a tablea such as below, I know its bad design having multifield value column but I'm really looking for a hack right now.
Student | Age | Classes
--------|------|----------
foo | 23 | classone, classtwo, classthree, classfour
bar | 24 | classtwo, classfive, classeight
When I run a simple select query as below, I want the results such a way that even occurrence of classtwo is displayed as class2
select student, classes from tablea;
I tried the replace() function but it doesnt work on multivalued fields >_<
You are in a tough situation and I can't think of a SQL solution for you. I think your best option would be to write a VB function that will take the string of data, parse it out (replacing) the returning you the updated string that you can update your data with.
I can cook up quite a few ways to solve this.
You can explode the mv by using Classes.Value in your query. This will cause one row to appear for each value in the query and thus you now can use replace on that. However, this will result in one separate row for each class.
So use this:
Select student, classes.Value from tablea
Or, for this example:
Select student, replace(classes.Value,"classtwo","class2") as myclass
from tablea
If you want one line, AND ALSO the multi value classes are NOT from another table (else they will be returning ID not text), then then you can use the following trick
Select student, dlookup("Classes","tablea","id = " & [id]) as sclasses
from tablea
The above will return the classes separated by a space as a string if you use dlookup(). So just add replace to the above SQL. I suppose if you want, you could also do replace on the space back to a "," for display.
Last but not least, if this those classes are coming from another table, then the dlookup() idea above will not work. So just simply create a VBA function.
You query becomes:
Select student, strClass([id]) as sclasses from tablea
And in a standard code module you create a public function like this:
Public Function strClass(id As Variant) As String
Dim rst As DAO.Recordset
If IsNull(id) = False Then
Set rst = CurrentDb.OpenRecordset("select Classes.Value from tableA where id = " & id)
Do While rst.EOF = False
If strClass <> "" Then strClass = strClass & ","
strClass = strClass & Replace(rst(0), "classtwo", "class2")
rst.MoveNext
Loop
rst.Close
Set rst = Nothing
End If
End Function
Also, if you sending this out to a report, then you can DUMP ALL of the above ideas, and simply bind the above to a text box on the report and put the ONE replace command around that in the text box control. It is quite likely you going to send this out to a report, but you did ask how to do this in a query, and it might be the wrong question since you can "fix" this issue in the report writer and not modify the data at the query level. I also think the replace() command used in the report writer would likely perform the best. However, the above query can be exported, so it really depends on the final goal here.
So lots of easy ways to do this.
I'm trying to query old Access database tables and compare them with SQL Server tables.
They often don't have primary keys, or they have extra fields that had some purpose in the nineties, etc., or the new tables have new fields, etc.
I need to find records - based on a set of fields specified at runtime - that are in one table but not another.
So, I do this kind of query all the time in SQL, when I'm comparing data in different tables:
dim fields_i_care_about as string = "field1, field2, field3"
'This kind of thing gets set by a caller, can be any number of fields, depends on the
'table
dim s as string= ""
dim flds = fields_i_care_about.split(",")
for i as integer = 0 to ubound(flds)
if s > "" then s += " AND "
s += " dysfunctional_database_table." & flds(i) & "=current_database_table." & flds(i)
next
s = "SELECT * from dysfunctional_database_table where not exists (SELECT * from current_database_table WHERE " & s & ")"
====
I'm trying to do this using Linq because it seems like some of the datatype problems with two different database types become less of a headache,
but I'm new to Linq and totally stuck.
I got as far as this:
Put old and new tables into datatables as dt1 and dt2
Dim new_records = _
From new_recs In dt2.AsEnumerable
Where Not ( _
From old_recs In dt1.AsEnumerable Where old_recs(field1) = new_recs(field1) AndAlso old_recs(field2) = new_recs(field2)).Any
Select new_recs
But I can't figure out how to put this part in on the fly -
old_recs(field1) = new_recs(field1) AndAlso old_recs(field2) = new_recs(field2)
So far I've tried:
putting the fields I want to compare and making them a string and just putting that string in as a variable ( I thought I was probably cheating, and I guess I was)
dim str = old_recs(field1) = new_recs(field1) AndAlso old_recs(field2) = new_recs(field2)
From new_recs In dt2.AsEnumerable
Where Not ( _
From old_recs In dt1.AsEnumerable Where str).Any
Select new_recs
It tells me it can't convert a Boolean -
Is there any way to do this without Linq expressions? They seem far more complex than what I'm trying to do here, and they take a lot of code, and also I can't seem to find examples of Expressions where we're comparing two fields in a subquery.
Is there a simpler way? I know I could do the usual EXISTS query using JOIN or IN - in this case I don't need the query to be super fast or anything. And I don't need to use a DataTable or DataSet - I can put the data in some other kind of object.
So I found a lot of sample code that used MethodInfo and reflection and things like that, but I couldn't get any of it to work - these Datarows have a Field method but it requires that you add an (of object) argument before the field name argument and that's tricky to do.
So I'm not sure if this solution is the most efficient way, but at least it works. I'd be interested in finding out whether this way of doing it is efficient and why or why not. It seemed like most people used reflection to do this kind of thing, but I couldn't get that working properly and anyway what I'm trying to do is pretty simple while those methods were pretty complex. I suppose I'm doing Linq with a SQL mindset, but anyway it works.
Dim f As Func(Of DataRow, DataRow, String, Boolean) = Function(d1 As DataRow, d2 As DataRow, s As String)
Dim fields = Split(s, ",")
Dim results As Boolean = True
For k As Integer = 0 To UBound(fields)
Dim obj = DataRowExtensions.Field(Of Object)(d1, fields(k))
Dim obj2 = DataRowExtensions.Field(Of Object)(d2, fields(k))
If obj <> obj2 Then results = False : Exit For
Next
Return results
End Function
Dim new_records = _
From new_recs In dt2.AsEnumerable.AsQueryable()
Where Not ( _
From old_recs In dt1.AsEnumerable.AsQueryable Where f(old_recs, new_recs, id_key)).Any
Select new_recs
Try
Return new_records.CopyToDataTable
Catch ex As Exception
Stop
End Try
I am populating a DataGrid with the following LINQ code :
Dim myClients = From p In dc.Persons _
Select p
I can navigate my DataGrid, make changes and then click on a button that calls
dc.SubmitChanges()
All of this works well and updates SQL Server.
I then wanted to add a single additional column that would display a calculated age based on a Function. I used the following code to create a PersonAge column and it worked.
Dim myClients = From p In dc.Persons _
Select New With {p.PersonID, _
p.PersonName, _
p.PersonGender, _
.PersonAge = CalcCurrentAge(p.PersonDOB, p.PersonFirstContactDate, p.PersonFirstContactAge) _
}
However, I noticed that I can no longer successfully save any updates back to SQL.
So my question is, how can I take the simplicity of the first LINQ code which saves updates correctly, and mix it with the second LINQ code which includes the PersonAge column to create an updatable DataGrid with a calculated age column?
Make your calculation for your data column in your DataGrid, rather than in the Linq statement.
http://www.dotnetjohn.com/articles.aspx?articleid=18
Given a datatable, I wish to output an IEnumerable type (dictionary(of T) would be perfect, otherwise a datatable would be acceptable) that provides an aggregation of the data within the datatable.
In SQL I would write the query as such:
select groupByColumn, sum(someNumber) from myTable group by groupByColumn
In VB.NET the closest I have got to this (achieved using information here) is:
' dt is a datatable containing two columns, referred to by index in p below
Dim q = From p In dt Group p By p(0) Into Sum(p(1)) Select p(0), SumOfNumber = Sum
However I receive error: "Range variable name can be inferred only from a simple or qualified name with no arguments." on the p(0) element.
Therefore my question is as follows:
How can I resolve this error?
How do I process the result (q) as an IEnumerable type?
Life isn't made any easier because I'm using Linq in unfamiliar vb.net. Many examples are in C#, but I haven't really come across anything suitable even in C#.
Resolved: I had to alias the columns returned.
Dim q = From p In dt
Group p By transactionTypeName = p(0) _
Into totalForType = Sum(Convert.ToDouble(p(1))) _
Select transactionTypeName, totalForType
Also note that I had to do a conversion on the value that I was summing because being a dynamically returned datatable didn't have the column type specified.
Hint found here because vb.net oh so helpfully gives us a different error message to C#'s "Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access."
For completeness, results are processed as below:
For Each item In q ' no need for defining item as a type (in C# we'd use the var keyword)
If item.totalForType = magicNumber Then
'do something
Else
'do something else
End If
Next