Saturday, June 11, 2011

Dynamically Iterate over a list of tables or views and export to flat files.

I recently came across an interesting Question In EE and was puzzled about how to achieve that using SSIS out of the box tasks, which was impossible as SSIS can;t use on the fly columns in the source or the destination.

SO definitely only could be done using a script task, but that wasn't really my favorite part, I'm the worst when it comes to that.

Anyway because I had some past experience as developing ASP pages using vb.net, so quickly came to my mind to build aDataGrid using a SQL query, then export the grid to a text file, which worked fine, The I came across the DataReader which is a neater and easier way.

So here I'm going to demonstrate how to Iterate over a list of views which has different structure to flat file using Script Task.

I'll be using the famous "AdventureWorksDW2008R2" DB for SQL 2008 and  "AdventureWorks" for SQL 2005 which could be downloaded for free here, The demo is being done on a windows Vista 64BIT machine, with SQL and VS 2008 installed. but there shouldn't be any version different if you're using SQL 2005.

Alright enough talking....

For SQL server 2008 Users......

1-The first step is to identify what are the views that we be exporting.


 
 


2-Check the columns count for each of them, just to illustrate the different in structure.

 
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SELECT A.name AS ViewName
  , count(B.TABLE_NAME) AS ColCount
FROM
 sys.objects AS A
 LEFT OUTER JOIN
  INFORMATION_SCHEMA.COLUMNS AS B
  ON A.name = B.TABLE_NAME
GROUP BY
 A.name
  , A.type
HAVING
 (A.type = 'v')
ORDER BY
 ColCount DESC


3-I'll create 4 Variables, I love to always to the proper naming convention to tell the data type of the variable.

 
 
Variables
Variables
 


A-Variable "ObjAllViews" will hold back the result set which has all the views' Names.
B-Variable "StrDelimiter"   will hold the delimiter that you want to use between columns, I love to use the Vertical Line "|" because most of our data has commas in it, you can get it by pressing (SHIFT + \ )
C-Variable "StrViewName" will hold each individual view.
D-Variable "StrFilePath" will hold the desired path to save the files.

4-Create a connection to your server, in my case it's 'localhost' as I've my testing SQL server on the same machine, and I named the connection 'Localhost', take note of naming the connection because it's mentioned later in the script task.

oh...so now you get the idea?  we will use the "Execute SQL Task" to get us the list of the views that exists in that table into "ObjAllViews"  variable, then we will use "Foreach Loop Container" to shred resultset from "ObjAllViews"  variable to each individual view name into "StrViewName" variable .

Then inside the "Foreach Loop Container" we will place a "Script Task" that will do the trick for us.

  

Now let's go over each tasks and how it's configured....

1-The control flow and the connection

 
ControlFlow and connection
ControlFlow and connection
 



2-Execute SQL Task

 
 
EST1
EST1
 

 
 
 


3-Foreach Loop Container

 
 
FEL1
FEL1
 

 
 
 


4-Script Task , Thanks for SIVA for helping me with the counter code.

 
 
 
 

5- add This code
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Imports System
Imports System.Data
Imports System.Math
Imports Microsoft.SqlServer.Dts.Runtime
Imports System.Data.OleDb
Imports System.Data.SqlClient
Imports System.IO

<System.AddIn.AddIn("ScriptMain", Version:="1.0", Publisher:="", Description:="")> _
<System.CLSCompliantAttribute(False)> _
Partial Public Class ScriptMain
    Inherits Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTARTScriptObjectModelBase
    Enum ScriptResults
        Success = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Success
        Failure = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Failure
    End Enum
    Public Sub Main()

        'Variable collection to hold the variables
        Dim VarCol As Variables = Nothing

        'Lock the 3 variables for read
        Dts.VariableDispenser.LockForRead("User::StrViewName")
        Dts.VariableDispenser.LockForRead("User::StrDelimiter")
        Dts.VariableDispenser.LockForRead("User::StrFilePath")


        'Fille the Variable collection
        Dts.VariableDispenser.GetVariables(VarCol)

        'Getting the variables' values, so we can use it later
        Dim ViewName As String = VarCol("User::StrViewName").Value.ToString()
        Dim delimiter As String = VarCol("User::StrDelimiter").Value.ToString()
        Dim FilePath As String = VarCol("User::StrFilePath").Value.ToString()


        'Construct the file name, example output: D:\vTargetMail.TXT
        Dim FName As String = FilePath & ViewName & ".TXT"

        'Build our Query
        Dim Query As String = "SELECT * FROM " & ViewName


        'Using StreamWriter
        Dim writer As StreamWriter = Nothing

        'Use our OLEDB COnnection
        Dim connection As OleDbConnection = New OleDbConnection(Dts.Connections("Localhost").ConnectionString)
        Dim command As OleDbCommand = Nothing
        Dim reader As OleDbDataReader = Nothing

        Try
            'Checking for the file, delete if exist(you can append or rename with [File.Move(FName, Today() & "_" & FName)]
            If File.Exists(FName) Then
                File.Delete(FName)
            End If
            'Open the OLEDB connection
            connection.Open()

            'Run the query
            command = New OleDbCommand(Query, connection)
            reader = command.ExecuteReader()

            If reader.HasRows Then

                'Stream Writer using the FNAME that we declared erlier
                writer = New System.IO.StreamWriter(FName)
                While reader.Read()

                    'Counter to get the columns number
                    Dim counter As Integer = 0
                    Dim fieldCount As Integer = reader.FieldCount - 1

                    While counter <= fieldCount
                        If counter <> fieldCount Then

                            writer.Write(reader(counter).ToString() & delimiter)
                        Else
                            writer.WriteLine(reader(counter).ToString())
                        End If
                        counter += 1
                    End While
                End While
            End If
        Catch ex As Exception
            Dts.Events.FireError(1, "", "Something Wrong happened!!!", "", 0)
        Finally
            connection.Close()
            writer.Close()
        End Try
        Dts.TaskResult = ScriptResults.Success
    End Sub
End Class


And The results .........

 
 
 



For SQL 2005 users...

We need to change the script task, also the SQL query too as follow:

1- change the SQL query to
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SELECT  (sys.schemas.name + '.' + sys.objects.name) AS ViewName
FROM    sys.objects 
INNER JOIN sys.schemas ON sys.objects.schema_id = sys.schemas.schema_id
Where type ='v'


2- and the script task as shown here
 
 
scripttask2005
scripttask2005
 


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Imports System
Imports System.Data
Imports System.Math
Imports Microsoft.SqlServer.Dts.Runtime
Imports System.Data.OleDb
Imports System.Data.SqlClient
Imports System.IO

Public Class ScriptMain

    Public Sub Main()

        'Variable collection to hold the variables
        Dim VarCol As Variables = Nothing

        'Lock the 3 variables for read
        Dts.VariableDispenser.LockForRead("User::StrViewName")
        Dts.VariableDispenser.LockForRead("User::StrDelimiter")
        Dts.VariableDispenser.LockForRead("User::StrFilePath")

        'Fille the Variable collection
        Dts.VariableDispenser.GetVariables(VarCol)

        'Getting the variables' values, so we can use it later
        Dim ViewName As String = VarCol("User::StrViewName").Value.ToString()
        Dim delimiter As String = VarCol("User::StrDelimiter").Value.ToString()
        Dim FilePath As String = VarCol("User::StrFilePath").Value.ToString()

        'Construct the file name, example output: D:\vTargetMail.TXT
        Dim FName As String = FilePath & ViewName & ".TXT"

        'Using StreamWriter
        Dim writer As StreamWriter = Nothing

        'Try
        'Checking for the file, delete if exist(you can append or rename with [File.Move(FName, Today() & "_" & FName)]
        If File.Exists(FName) Then
            File.Delete(FName)
        End If

        'Open the OLEDB connection
        Dim connection As New OleDbConnection("Provider=SQLOLEDB;Data Source=Localhost;Initial Catalog=AdventureWorks;Integrated Security=SSPI;")
        connection.Open()
        Dim Query As String = "SELECT * FROM " & ViewName
      
        Dim command As OleDbCommand = New OleDbCommand(Query, connection)

        Dim reader As OleDbDataReader = command.ExecuteReader()

        If reader.HasRows Then

            'Stream Writer using the FNAME that we declared erlier
            writer = New System.IO.StreamWriter(FName)
            While reader.Read()

                'Counter to get the columns number
                Dim counter As Integer = 0
                Dim fieldCount As Integer = reader.FieldCount - 1

                While counter <= fieldCount
                    If counter <> fieldCount Then

                        writer.Write(reader(counter).ToString() & delimiter)
                    Else
                        writer.WriteLine(reader(counter).ToString())
                    End If
                    counter += 1
                End While
            End While
            reader.Close()
        End If

        connection.Close()
        writer.Close()
        'Catch ex As Exception
        '    Dts.Events.FireError(1, "Nasty", "Something Wrong happened!!!", "", 0)
        '    Throw ex
        'Finally

        'End Try
        Dts.TaskResult = Dts.Results.Success
    End Sub
End Class



Solution assumptions:

1-You're using SQL 2008 or SQL 2005.
2-Server name is "Localhost" hosted locally, otherwise, please change that.
3-You have write access to your D:\  Drive.
4-For SQL 2008 you have installed "AdventureWorksDW2008R2" DB and  "AdventureWorks" for SQL 2005. 


That's it...I hope my article helps someone to be more dynamic and flexible in SSIS and over come some of the Data Flow limitations.

Also I'm open to discussions and comments if you have a better way to do it.

The final package for SQL 2008 can be FOUND HERE   and for SQL 2005 FROM HERE