Join two queries from different data sources using VB.NET - sql

Question

I have two queries. One is an Oracle query, and one is a SQL Server query.
Oracle Columns: ID, Subject, Course
SQL Server Columns: ID, Recommended Subject, Recommended Course
I would like to join the two queries on ID. I need to find out which IDs have a subject that is not equal to the recommended subject or a course that is not equal to the recommended course. Then, display the results in a GridView.
Here's what I have tried to do so far. I have removed my SQL commands and connection strings.
Dim sConnectionString As String = ConfigurationManager.ConnectionStrings("sqlserver").ConnectionString
Dim sCN As New SqlConnection(sConnectionString)
Dim sCommandWrapper As SqlCommand = New SqlCommand("SQL", sCN)
Dim sDataAdapter As SqlDataAdapter = New SqlDataAdapter
sDataAdapter.SelectCommand = sCommandWrapper
Dim pConnectionString As String = ConfigurationManager.ConnectionStrings("oracle").ConnectionString
Dim pCN As New OleDbConnection(pConnectionString)
Dim pCommandWrapper As OleDbCommand = New OleDbCommand("SQL", pCN)
Dim pDataAdapter As OleDbDataAdapter = New OleDbDataAdapter
pDataAdapter.SelectCommand = pCommandWrapper
Dim stopDS As DataSet = New DataSet()
sDataAdapter.Fill(stopDS, "Recommendations")
pDataAdapter.Fill(stopDS, "Registrations")

Answer 1

Since you have your two results in a DataSet, you can define a relationship between the two tables using the DataSet.Relations property:
stopDS.Relations.Add(
"ID2ID",
stopDS.Tables("Recommendations").Columns("ID"),
stopDS.Tables("Registrations").Columns("ID")
)
You can then get the matching rows from either end of the relationship (apologies if I got the relationship the wrong way around!):
Dim rows() As DataRow = stopDS.Tables("Recommendations").Rows(0).GetChildRows("ID2ID")
Dim row As DataRow = stopDS.Tables("Registrations").Rows(0).GetParentRow("ID2ID")
' Can also use .GetParentRows(...) for an array.
Here is a complete example console app:
Module Module1
Sub Main()
Dim t1 = New DataTable()
t1.TableName = "Names"
t1.Columns.Add("ID", GetType(Integer))
t1.Columns.Add("Name", GetType(String))
Dim t2 = New DataTable()
t2.TableName = "Addresses"
t2.Columns.Add("ID", GetType(Integer))
t2.Columns.Add("Address", GetType(String))
Dim r As DataRow = Nothing
r = t1.NewRow()
r("ID") = 1
r("Name") = "Bob"
t1.Rows.Add(r)
r = t1.NewRow()
r("ID") = 2
r("Name") = "Joe"
t1.Rows.Add(r)
r = t1.NewRow()
r("ID") = 3
r("Name") = "Sue"
t1.Rows.Add(r)
r = t2.NewRow()
r("ID") = 1
r("Address") = "1 Main St"
t2.Rows.Add(r)
r = t2.NewRow()
r("ID") = 3
r("Address") = "2 Any St"
t2.Rows.Add(r)
Dim ds = New DataSet()
ds.Tables.Add(t1)
ds.Tables.Add(t2)
' Define relationship between the ID columns
ds.Relations.Add(
"NameToAddress",
ds.Tables("Names").Columns("ID"),
ds.Tables("Addresses").Columns("ID"))
For Each nameRow In t1.AsEnumerable()
Console.WriteLine("Name: {0}", nameRow.Field(Of String)("Name"))
For Each addrRow In nameRow.GetChildRows("NameToAddress")
Console.WriteLine("--Addr: {0}", addrRow.Field(Of String)("Address"))
Next
Next
Console.WriteLine("==========")
For Each addrRow In t2.AsEnumerable()
Console.WriteLine("Addr: {0}", addrRow.Field(Of String)("Address"))
Dim pr = addrRow.GetParentRow("NameToAddress")
If pr IsNot Nothing Then
Console.WriteLine("++Name: {0}", pr.Field(Of String)("Name"))
End If
For Each nameRow In addrRow.GetParentRows("NameToAddress")
Console.WriteLine("--Name: {0}", nameRow.Field(Of String)("Name"))
Next
Next
Console.ReadLine()
End Sub
End Module
The results are:
Name: Bob
--Addr: 1 Main St
Name: Joe
Name: Sue
--Addr: 2 Any St
==========
Addr: 1 Main St
++Name: Bob
--Name: Bob
Addr: 2 Any St
++Name: Sue
--Name: Sue

Answer 2

I really like Mike's approach, but let me suggest another one and you can choose whichever more suitable for you.
You can set up a linked server to your Oracle database. It is described in this answer. Alternatively you can follow this article.
Then simply join the two tables and get the results:
SELECT * FROM SqlTable s
INNER JOIN OracleServer.OracleDB..OracleTable o ON o.ID = s.ID
AND (s.Course != o.[Recommended Course] OR s.Subject != o.[Recommended Subject])
Unfortunately I don't have oracle installed to completely test this myself, but I hope you get in the direction.