SQL Server: Data transfer for Excel using Linked Server
Introduction
I will demonstrate yet another way to perform data transfer to and from an excel file using a Linked Server in SQL Server 2008. In this demo I will show you how to:
- Create a Linked Server using Excel as the data server
- Import data to a SQL Server table from a spreadsheet
- Export data to a spreadsheet from a SQL Server table
Create a Data Source
As the first step in this process I have created an Excel file with a spreadsheet named “Employee”, followed by defining the headers and inserting 5 records as showing in following illustration:
Create a Linked Server
Now that we have a data source let us create a linked server using an the Excel file created in the previous step as the data source. Open SQL Server Management Studion (SSMS) and expand “Server Objects” under the intended SQL Server, to find the Linked Servers item.Right click on Linked Servers and click on “New Linked Server” to see following dialog box. EXCEL_LINKED_SERVER is the name that I have chosen to call this linked server. Then we need to populate the Provider, Product Name, Data Source and Provider String like in this example and click the OK button.
A linked server should have been created successfully at this time. Right click on the “Linked Server” tree view item and click on refresh to see the newly created linked server. Expand the linked server to see the Exployee$ spreadsheet under the list of tables.
Import Data
At this point you should be able to access the Excel spread sheet just like any other SQL Server database table. Let us import data into a table named DataFeed in the Demo database. It is important to note that the spreadsheet name in the SQL query has to be accessed only by preceding spreadsheet name with “…” Only one dot is used to represent the current database, two dots to represent another database in the SQL Server instance and three dots represent a Linked Server. When we would have ran the following SQL query, a table named “DataFeed” would have been created and 5 records from this table would be displayed in the results pane.
Export Data
Let us insert a couple of records into the DataFeed table that was created in the above step, followed by exporting those two rows to the spreadsheet. When the following query us run, you will observe that the spread sheet will have 7 records.
Now Let us look at the new data in the spreadsheet:
Sample Code: Xml validation using XSD
Starting today I will post some useful code snippets, samples to perform simple coding tasks. First in this series is a code sample on how to validate an XML file using an XSD file.
Import the following namespaces
using System; using System.IO; using System.Xml; using System.Xml.Schema; using System.Xml.XPath;
Validate a XML File
public static void ValidateXmlFile(string XMLfilename, string XSDfilename)
{
//make sure the file exists
if (!File.Exists(XMLfilename))
{
Console.WriteLine("Error: XML Data File '{0}' not found.", XMLfilename);
return 0;
}
//Standard schema validation first
XmlDocument document = new XmlDocument();
try
{
document.Load(XMLfilename);
}
catch (XmlException xmle)
{
Console.WriteLine("!!!Error!!!\r\nXML Validation Failure: {0}\r\n\r\n", xmle.Message);
return 0;
}
document.Schemas.Add(XSDfilename, "");
ValidationEventHandler validation = new ValidationEventHandler(SchemaValidationHandler);
document.Validate(validation);
}
Define a Schema Validation Handler
private static void SchemaValidationHandler(object sender, ValidationEventArgs e)
{
switch (e.Severity)
{
case XmlSeverityType.Error:
Console.WriteLine("Schema Validation Error: {0}", e.Message);
break;
case XmlSeverityType.Warning:
Console.WriteLine("Schema Validation Warning: {0}", e.Message);
break;
}
return 0;
}
Dependency Injection: Unity Application Block
In this post I will show you how to use Microsoft Unit Application Block to achieve Dependency Injection. We will see the two methods of configuring the IOC container, firstly the “.config” way and then the “inline” method. Let us take a look at the following code snippet and see how this code can be improved.
class Program
{
static void Main(string[] args)
{
Service svc = new Service();
svc.Print();
}
}
public class Service
{
public void Print()
{
Employee empl = new Employee();
empl.PrintEmployeeTitle("Test Employee");
}
}
public class Employee
{
public void PrintEmployeeTitle(string name)
{
Console.WriteLine("Employee Name: {0}, Title:{1}", name, "Some Title");
}
}
What does this code do?
The above code snippet if from a console application, where we are creating an instance of the Service class and are calling the Print method. The Print method in turn instantiates the Employee class and then calls the PrintEmployeeTitle method of the Employee class to print the employee name and title. The PrintEmployeeTitle method writes the name and title of an employee to the console.
What is wrong?
Nothing. While there is nothing wrong with this code, if we closely observer, we can notice that the Employee class instance could not exist without an instance of the Service class. Basically they both are tightly coupled, meaning to say we can only have one implementation of the Employee class to be consumed by the Service class at any given instance of time.
What if we have a scenario when we want to test more than one implementation of the Employee class or if the Employee class implementation is a work-in-progress? Here is where Dependency Injection design pattern comes to our rescue. I hope I have set some context before I explaining about DI and its implementation.
Solving the problem
Decoupling the Employee class life cycle management from the Service class is the primary objective. The advantage of decoupling the Employee class are that 1) we will be in a position to provide multiple implementations to the Employee class 2) be able to select the kind of implementation that is suitable for our purpose and 3) manage the life cycle of the Employee class. We define an interface IEmployee with one method PrintEmployeeTitle and define two implementations for this demo purpose. The first implementation is what we already had above and the second is a MockEmployee Class.
public class Employee : IEmployee
{
public void PrintEmployeeTitle(string name)
{
Console.WriteLine("Employee Name: {0}, Title:{1}", name, "Some Title");
}
}
public class MockEmployee : IEmployee
{
public void PrintEmployeeTitle(string name)
{
Console.WriteLine("Employee Name: {0}, Title:{1}", name, "Some MOCK Title");
}
}
public interface IEmployee
{
void PrintEmployeeTitle(string name);
}
Let us see how we can delegate the Employee class instantiation to the client (Class:Program; Method: Main) and then inject the Employee object into the Service object.
Dependency Injection
Service class has a dependency on the Employee class and our objective here is inject this dependency into the Service class from the Client. Dependency injection is a software design pattern that allows a choice of component to be made at run-time rather than compile time [2]. One way to achieve this is via passing the Employee object reference to the Service class constructor like in the code below:
class Program
{
static void Main(string[] args)
{
Employee empl = new Employee();
Service svc = new Service(empl);
svc.Print();
}
}
public class Service
{
private IEmployee empl;
public Service(IEmployee empl)
{
this.empl = empl;
}
public void Print()
{
empl.PrintEmployeeTitle("Test Employee");
}
}
Another way of injecting the Employee reference into the Service object is via setting the instance of Employee class to an I IEmployee property of the Service class.
class Program
{
static void Main(string[] args)
{
Employee empl = new Employee();
Service svc = new Service();
svc.empl = empl;
svc.Print();
}
}
public class Service
{
IEmployee _empl;
public IEmployee empl
{
set
{
this._empl = value;
}
}
public void Print()
{
_empl.PrintEmployeeTitle("Test Employee");
}
}
We have so far been able to decouple the Service class and the Employee class, however we still have to create an instance of the Employee class to implement dependency injection. Any change in to the Employee class creation mechanism with require a code change and also a code recompile. This is the point where IOC framework comes handy in automating the creation and injection of the dependency via just one configuration.
Inversion of control
In software engineering, Inversion of Control (IoC) is an object-oriented programming practice where the object coupling is bound at run time by an assembler object and is typically not known at compile time using static analysis [1]. Like discussed earlier we are going to transfer the control of creating the Employee object to the IOC framework rather than keeping it with the Client, mean to say we are performing an “Inversion of Control”.
The configured entities are loaded into an IOC container at run-time and will be injected into the appropriate classes. We can implement .Net Dependency Inject using any one of the following IOC containers:
Microsoft Unity IoC Container
Now let us look at the two ways of configuring and implementing DI using Microsoft Unity Container. Before we can use the Unity container you have to download and install the Microsoft Unit Application Block from the Microsoft Patterns and Practices website. The dll’s necessary for this implementation can be found under the “Drive:/Program Files/Microsoft Unity Application Block x.0/Bin/” folder and should be added as references to your project.
Please accept my apologies for a very crude/rude representation of the client (Class: Program, Method: Main) being able to select one of the three implementations of the Employee class use Dependency Injection via an IOC container.
Application Configuration File
When we have to implement DI using the Application Config file, we have to define Unity block section, define a container and register that namespace and the Class that is getting DI’ed.
<configSections> <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,Microsoft.Practices.Unity.Configuration" /> </configSections> <unity xmlns="http://schemas.microsoft.com/practices/2010/unity"> <alias alias="singleton" type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager, Microsoft.Practices.Unity" /> <container name="TestService"> <register type="UnityFrameworkDemo.IEmployee, UnityFrameworkDemo" mapTo="UnityFrameworkDemo.MockEmployee, UnityFrameworkDemo"> <lifetime type="singleton" /> </register> </container> </unity>
I had to also add a reference of the System.Configuration namespace to the project. Once we have this configuration all set, we have to update the client to 1) load the container that we defined in the configuration and 2) generate the Service class based on the configuration that we have defined:
class Program
{
static void Main(string[] args)
{
try
{
container.LoadConfiguration("TestService");
svc = container.Resolve();
if (svc != null)
svc.Print();
else
Console.WriteLine("Could not load the Service Class");
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
public class Service
{
IEmployee _empl;
public Service(IEmployee empl)
{
this._empl = empl;
}
public void Print()
{
_empl.PrintEmployeeTitle("Test Employee");
}
}
You would also have noticed that I have added a constructor that accepts parameter of IEmployee type to the Service class. The IOC framework will use this constructor to generate an instance of the Service class and will also pass a reference of the Employee class into the Service instance. Following is the output of using the default Employee implementation:
Now switching to the Mock Employee implementation from the default implementaion is as simple as updating the register element of the configuration with the MockEmployee class name and then we get the following output
Inline
Lastly let us look at how we can configure an implementation inside the client instead of in the application config file. Basically you have to register the Interface and the implementation with the container in the client and your client is ready to make a call to the Service instance methods like shown in the code below:
container.RegisterType();
svc = container.Resolve();
if (svc != null)
svc.Print();
Unity framework basically provides a fantastic approach to decouple the application layer code. You can define several containers and register several classes with the container and be able to enjoy the flexibility by implementing Dependency Injection using the Unity IOC container.
Happy Fourth of July !
References:
1. Inversion of Control – IOC – Wikipedia
2. Dependency Injection – Wikipedia
PSExec: Execute batch files remotely
PsExec is a light-weight telnet-replacement that lets you execute processes on other systems, complete with full interactivity for console applications, without having to manually install client software. PsExec’s most powerful uses include launching interactive command-prompts on remote systems. [1]
Ad-hoc execution of batch files from on server remotely using psexec is an easy and a time saving activity. Here is an example of how to execute a batch file using psexec:
psexec \\REMOTESERVERNAME -u [USERNAME] -p [PASSWORD] /accepteula -d -i cmd /c D:\FILE.bat
cmd /c – this gives a context to the psexec to
/accepteula – this switch will simulate the accepting eula agreement.
D:\ – drive on the remote server
-d – Don’t wait for application to terminate. Only use this option for non-interactive applications.
-i – Run the program so that it interacts with the desktop of the specified session on the remote system. If no session is specified the process runs in the console session.
The output of the execution would be that cmd exited on with error code 0.
Update: 09-13-2012
All of a sudden the above command started to fail. At this point my guess is that some network settings/permissions must have got updated preventing the command to execute successfully. Following is the error
Error: The parameter is incorrect.
Fix: psexec \\REMOTESERVERNAME -u [USERNAME] -p [PASSWORD] /accepteula -h cmd /c D:\FILE.bat
References:
1. PsExec v1.98
EF4: Searching Japanese text won’t work
Problem: EF4 does not to return any data when searching for Japanese names from a user table.
Setup: The web application layers use the following technologies
ASP.Net <—-> Business Layer <—-> EF 4 <—-> SQL Server 2008
Stored procedures are being employed for data retrieval operations. All the stored procedure parameters are of nvarchar type and the data is stored in the tables as nvarchar type as well.
Troubleshooting:
1. Stored procedures work fine in SSMS.
exec sp_search_user N'Japanese text', N'Japanese Text'
Here is what I got from SQL Profiler: exec sp_search_user ‘??’, ‘??’
The Japanese text got replaced with ??
2. Adding RequestEncoding=”utf-8″ ResponseEncoding=”utf-8″ attributes to the Page directive had no impact on the outcome.
3. The data reached the data access layer intact and here is the code that makes a call to the function import:
public IQueryable SearchUsers(string first_name, string last_name)
{
//db is the database context
ObjectResult SearchResult = db.SearchUsers(first_name, last_name);
IQueryable users = from tmp in SearchResult.AsQueryable() select tmp;
return users;
}
4. I have also verified that the East Asian Language pack was indeed installed on the application server.
Solution: Apparently, I found out (with help from TinMgAye) that the edmx file could not update the data types of the stored procedure to nvarchar from varchar.
There could be a flaw inside the edmx definition about nvarchar and varchar. How we can verify is, firstly make sure your stored procedure in SQL is accepting input parameter as nvarchar. Then try to remove all the function definition and stored procedure from edmx and update edmx again to include the stored procedure and function. Or you know what you are doing mode…. Right click edmx >> Open with >> choose XML editor, then look for stored procedure name in function tag and check the parameter type there.
<Function Name="Your SP Name"><Parameter Name="Para Name" Type="nvarchar" Mode="In" /> </Function>
Cheers !
SQL Server: Get only the date and/or only the time part
In this post I want to highlight some very useful Microsoft SQL Server System functions that can used to fetch datetime, only the date and only the time.
Fetch various date and times
SELECT SYSDATETIME() [DATE TIME] ,SYSDATETIMEOFFSET() [DATE TIME OFFSET] ,SYSUTCDATETIME() [UTC DATE TIME] ,CURRENT_TIMESTAMP [CURRENT_TIMESTAMP] ,GETDATE() [DATE] ,GETUTCDATE() [UTC DATE];
Fetch only the date part
SELECT CONVERT (date, SYSDATETIME()) [DATE] ,CONVERT (date, SYSDATETIMEOFFSET()) [DATE OFFSET] ,CONVERT (date, SYSUTCDATETIME()) [UTC DATE] ,CONVERT (date, CURRENT_TIMESTAMP) [CURRENT DATESTAMP] ,CONVERT (date, GETDATE()) [DATE] ,CONVERT (date, GETUTCDATE()) [UTC DATE];
Fetch only the date part
SELECT CONVERT (time, SYSDATETIME()) [SYS TIME] ,CONVERT (time, SYSDATETIMEOFFSET()) [ TIME OFFSET] ,CONVERT (time, SYSUTCDATETIME()) [UTC TIME] ,CONVERT (time, CURRENT_TIMESTAMP) [CURRENT_TIMESTAMP] ,CONVERT (time, GETDATE()) [TIME] ,CONVERT (time, GETUTCDATE()) [UTC TIME];
