Question

I have a database with two tables. Advertisements and Records as it’s foreign key. I need to count how often a record of an advertisement occurs and order by ascending.

I am assuming that I have to use a combination of a join and a group by clause to accomplish this. It just isn’t working the way I would like. Below is the code I have so far.

    Public Shared Function SortAdsByHitCount() As DataTable
    Dim dt As New DataTable

    Try
        Using context As New QREntities()
            Dim ads = (From advertisement In context.QRAdvertisements
                      Join record In context.QRRecords On advertisement.adId Equals record.adId
                      Select advertisement.adId, advertisement.adRedirectUrl, advertisement.adType, advertisement.adData, count = record
                      Order By AdData Ascending).ToList()

            'Dim ads = (From advertisement In context.QRAdvertisements
            '          Group advertisement.adId By advertisement.adId Into Group _
            '          Order By Group.Count() Ascending _
            '          Select Advertisement.AdRedirectUrl, Advertisement.AdType, Advertisement.AdData, Count = Group.Count()).ToList()

            'Set the column headers and their accepted data types
            dt.Columns.Add("adId", GetType(Integer))
            dt.Columns.Add("adRedirectUrl", GetType(String))
            dt.Columns.Add("adType", GetType(String))
            dt.Columns.Add("adData", GetType(String))
            dt.Columns.Add("hitCount", GetType(Integer))

            For Each a In ads
                dt.Rows.Add(a.adId, a.adRedirectUrl, a.adType, a.adData, a.Count)
            Next
        End Using
    Catch ex As Exception
        Return Nothing
    End Try

    Return dt
End Function

I basically need 4 rows from one table and I just include the count of the occurrence from the other. The advertisement datarow must know how many times it has been represented in the records table. So essentially, the gridview/listview would show the user a list of ads sorted by the frequency that that ad has been used.

Ex:
Advertisements

Ad id   Ad Type         Ad Date          Ad Occurrence

1       Automotive      13/12/2012       10
2       Personal        10/12/2012       5
3       Retail          02/11/2012       3

Answer 1

Here you need to be using a grouping function so you have access to the .Count() extension of the group. To do this in static syntax would look like this:

Dim ads = (From advertisement In context.QRAdvertisements
                      Group Join record In context.QRRecords 
                      On advertisement.adId Equals record.adId 
                      Into records = Group
                      Select advertisement.adId, advertisement.adRedirectUrl, advertisement.adType, advertisement.adData, count = records.Count()
                      Order By AdData Ascending).ToList()