The Northwind database is referenced online in sample code quite often. However, this renders the sample code useless to someone who doesn’t know what Northwind is or how to use it.

The Northwind database is basically just an example database that runs under SQL Server. This database is populated with data that represents an imaginary company’s sales data. It is a very common example database for SQL Server testing and sampling.

You might be wondering, what is SQL Server (though for your sake, I hope not). Well, SQL Server is Microsoft’s database software.

How do I know if SQL is installed?
If you have Visual Studio 2008 installed, you probably have SQL Server 2008 installed and you don’t even know it.

You can go to Add / Remove Programs and look for Microsoft SQL Server.

Or you can check for the services.

Or if you aren’t good with the GUI, you can open a command prompt and run this command to see if you have the SQL services:

If you don’t see the services ouptut, you don’t have SQL Server Express installed. If you do have it, it is installed.

SQL Server is installed, now where do I get the Northwind Database?
Well, this was a struggle even for me. All the posts say the database creation script was installed with Visual Studio, but I sure don’t have any database creation scripts installed.

So I searched the web and Microsoft’s site for a while.

I finally found this link, but not until after about an hour of searching, hopefully this saves you some time.
http://www.codeplex.com/Wikipage?ProjectName=SqlServerSamples

So as of 3/4/2010, there was not “new” Northwind database, just and old one for SQL 2000. Which is fine because that old database is what most the sample code you find will be using.

I clicked on the Download link next to SQL Server 2000 Sample DBs.
I downloaded a ZIP file.
I extracted it.
I found the instnwnd.sql script among the extracted files.

How do I use the instnwnd.sql file to install the Northwind Database
This instnwnd.sql is nothing more than SQL script that will install the Northwind database for you. Well, you basically need your SQL server to run this script file and that is it.

If you have SQL Server Management Studio, just open it up and connect to your database, then File | Open the script and run it. But maybe you don’t know what SQL Server Management Studio is, let alone how to open it.

Sound easy right.

Well, everything sounds easy to some one who knows exactly how to do it, but if you don’t now how, it doesn’t sound easy. If you are among those that are hearing about this for the first time, let me help you.

Well, every server that has SQL Server installed has a command line tool installed called sqlcmd.exe. Hey, if I give you a command line you can run it, even if you don’t know what is really going on.

So just open a command prompt and run this command:

Ok, the database installed now what?
Well, now you have the Northwind database installed.

From here you are one your own getting whatever sample code you have to connect to this database and compile.

Imagine you have a query such as the following:

SELECT * FROM User WHERE LastName='O'Conner'

INSERT INTO User (FirstName, LastName, UserName, Email) VALUES ('John','O'Conner','jo'conner','joconner@somedomain.tld')

Well, that is obviously not going to work, because the apostrophe or single quote in the name O’Conner is going to break the query syntax.

You have to have two single quotes to use a quote.

SELECT * FROM User WHERE LastName='O''Conner'

INSERT INTO User (FirstName, LastName, UserName, Email) VALUES ('John','O'Conner','jo''conner','joconner@somedomain.tld')

Ok, so there are two ways to make sure you have two quotes in C#:

1. You manage the query string yourself.
2. You use a DataTable and let it manage the query string for you.

Managing the query string yourself

Ok, the answer is simple. You need two single quotes next to each other.

Now, when you have single string, this is easy to do. You need to replace each instance of a single quote with two single quotes using this function which already exists for you:

string.replace(string inStringToBeReplaced, string inNewString)

Here is an example of doing it wrong, then fixing it. Step through this in a debugger.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SingleQuoteInSQL
{
    class Program
    {
        static void Main(string[] args)
        {
            string FirstName = "John";
            string LastName  = "O'Conner";
            string UserName  = "joconner";
            string Email     = "joconner@domain.tld";

            // Both these queries are broken because of the space.
            string strQuery1 = "SELECT * FROM User WHERE LastName='" + LastName + "'";
            string strQuery2 = "INSERT INTO User (FirstName, LastName, UserName, Email) VALUES (" +
                        "'" + FirstName + "'," +
                        "'" + LastName + "'," +
                        "'" + UserName + "'," +
                        "'" + Email + "')";

            // This will actually break your query too, because it will replace valid single quotes
            // with two single quotes.  You need to do this on the actually data strings.
            strQuery1 = strQuery1.Replace("'", "''"); //
            strQuery2 = strQuery1.Replace("'", "''");

            // Replace any intance of a single quote with two single quotes, ''.
            // IMPORTANT: Typing two single quotes ('') is not the same as a double quote (").
            FirstName = FirstName.Replace("'", "''");
            LastName = LastName.Replace("'", "''");
            UserName = UserName.Replace("'", "''");
            Email = Email.Replace("'", "''");

            // Both these queries are working now;
            strQuery1 = "SELECT * FROM User WHERE LastName='" + LastName + "'";
            strQuery2 = "INSERT INTO User (FirstName, LastName, UserName, Email) VALUES (" +
                        "'" + FirstName + "'," +
                        "'" + LastName + "'," +
                        "'" + UserName + "'," +
                        "'" + Email + "')";
        }
    }
}

Using a DataTable to manage this for you automagically

This actually looks like more work at first, but really when handling a lot of data, it is much more easy to code using DataTables and DataRows.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;

namespace SingleQuoteInSQL
{
    class Program
    {
        static void Main(string[] args)
        {
            string FirstName  = "John";
            string LastName  = "O'Conner";
            string UserName  = "joconner";
            string Email        = "joconner@domain.tld";

            // Create the connection
            string mConnectionString = "Data Source=ServerName; user id=UserName; password=pw; Initial Catalog=DatabaseName;";
            SqlConnection mSqlConnection = new SqlConnection(mConnectionString);

            // Create a data adapter, this is what does the magic.
            String mQueryForSqlDataAdapter = "Select * from TableName";
            SqlDataAdapter tmpSqlDataAdapter;
            SqlCommandBuilder tmpSqlCommandBuilder;
            DataTable tmpDataTable = new DataTable();
            tmpSqlDataAdapter = new SqlDataAdapter(mQueryForSqlDataAdapter, mSqlConnection);

            // Use the SqlDataAdapter to create a table with the right schema but no data
            tmpDataTable = tmpSqlDataAdapter.FillSchema(tmpDataTable, SchemaType.Mapped);

            // Create a SqlCommandBuilder
            tmpSqlCommandBuilder = new SqlCommandBuilder(tmpSqlDataAdapter);

            // Create a DataRow and populate it
            DataRow row = tmpDataTable.NewRow();
            row["FirstName"] = FirstName;
            row["LastName"] = LastName;
            row["UserName"] = UserName;
            row["Email"] = Email;

            // Add this row to the DataTable
            tmpDataTable.Rows.Add(row);

            // Write this to the database
            tmpSqlDataAdapter.Update(tmpDataTable);
        }
    }
}

Notice we didn’t have to do a string replace of ‘ for ”.

Simple question, simple answer

SQL Query to return the data

SELECT TABLE_NAME FROM DBName.INFORMATION_SCHEMA.Tables WHERE TABLE_NAME='Article'

How do I check this in C#?

As for how you check that in C#? You just make sure the Row count returned from the query is 1. See this article I have already posted.

How do I get the number of rows returned from a Microsoft SQL Query in C#?

The following example accomplishes this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace InsertToDatabase
{
	public class InsertToDatabase
	{
		string connectionString = @"Data Source = ServerName; user id=UserName; password=P@sswd!; Initial Catalog = DatabaseName;";
		string query = "INSERT INTO Users (Firstname, Lastname, Email) VALUES ('Jared','Barneck','Jared.Barneck@somedomain.tld')";
		SqlConnection connection = new SqlConnection(connectionString);
		SqlCommand command = new SqlCommand(query, connection);
		connection.Open();
		command.ExecuteNonQuery();
		connection.Close();
	}
}

What is the difference between a DataSet and a DataTable?
Here is a link to the MSDN class information for both:
DataSet Class
DataTable Class

So a DataTable is just a table.

However, a DataSet is a collection of tables that can have their data linked together with a DataRelation Class.

So when accessing a database, which should you use?
Well, if you only need a single table, then just use a DataTable.
However, if you need multiple tables and those tables may have some type of relationship, use a DataSet.

How do I get the number of rows returned from a SQL Query in C#?

Having used other languages where this is much simpler, I was surprised at how “not simple” this was in C#. I expected it to be a little more complex than in some scripting language such as PHP, but it was way more complex.

Here is how I do it:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;

namespace CountRows
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create a string to hold the database connection string
            string sdwConnectionString = @"Data Source = ServerName; user id=UserName; password=P@sswd!; Initial Catalog = DatabaseName;";

            // Create a string to hold the database connection string
            string query = "SELECT * FROM MyTable";

            // Pass both strings to a new SqlCommand object.
            SqlCommand queryCommand = new SqlCommand(query, sdwDBConnection);

            // Create a SqlDataReader
            SqlDataReader queryCommandReader = queryCommand.ExecuteReader();

            // Create a DataTable object to hold all the data returned by the query.
            DataTable dataTable = new DataTable();
            dataTable.Load(queryCommandReader);

            // The DataTable object has a nice DataTable.Rows.Count property that returns the row count.
            int rowCount = rowCount = dataTable.Rows.Count;
        }
    }
}

Now doing it this way, you also have the data available in the DataTable dataTable object so you don’t have to go to the database and get it again.

How I get the number of rows in a table using C#?

Here is a step by step:

Step 1 – Create a new class: (attached click here: SQLTableRowCounter.cs)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace SQLTableRowCounter
{
    class SQLTableRowCounter
    {
        private string mCountQuery;
        private SqlConnection mConnection;
        private int mNumberOfRows;

        public SQLTableRowCounter(String inTableName, SqlConnection inConnection)
        {
            mCountQuery = "SELECT COUNT(*) FROM " + inTableName;
            mConnection = inConnection;
            mConnection.Open();
            SqlCommand mCountQueryCommand = new SqlCommand(mCountQuery, mConnection);
            mNumberOfRows = (int)mCountQueryCommand.ExecuteScalar();
        }

        public int NumberOfRows
        {
            get { return mNumberOfRows; }
            set { mNumberOfRows = value; }
        }
    }
}

Step 2 – Now create the object and get the value:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;

namespace SQLTableRowCounter
{
    class Program
    {
        static void Main(string[] args)
        {
             string connectionString = @"Data Source = ServerName; user id=UserName; password=P@sswd!; Initial Catalog = DatabaseName;";
             SqlConnection connection = new SqlConnection(connectionString);
             SQLTableRowCounter qrc = new SQLTableRowCounter("TableName", connection);
             int numRows = qrc.NumberOfRows;
        }
    }
}